Neuroscience Lab Manual 2012

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MEID 936

NEUROSCIENCE LABORATORY SYLLABUS

BY

JOHN B. GELDERD, Ph.D.

The illustrations within the text of this laboratory syllabus were created by Joan Quarles.

Selected illustrations within the syllabus were modified from published illustrations byFrank Netter, MD with the permission of Novartis Medical Education, Whippany, NJ.



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TABLE OF CONTENTS

Introduction ………………………………………………………………. pp. 3 – 4

Gross Anatomy of the Brain …………………………………………… pp. 5 – 12

Meninges ………………………………………………………………….. pp. 13 – 14

Blood Supply ……………………………………………………………... pp. 15 – 19

CSF and Ventricles of the Brain ………………………………………. pp. 20 – 23

Introduction to the MacroscopicAnatomy of the Neuraxis ……………………………………………….. pp. 24 – 29

Ascending Sensory Pathways ………………………………………… pp. 30 – 33

Sensory Pathways for theAnterior 2/3 of the Head ………………………………………………... pp. 34 – 36

Pyramidal System ……………………………………………………….. pp. 37 – 40

Cranial Nerves ……………………………………………………………. pp. 41 – 50

Basal Ganglia …………………………………………………………….. pp. 51 – 55

Cerebellum …………….………………………………………………….. pp. 56 – 63

Vestibular System …….…………………………………………………. pp. 64 – 65

Auditory System …………………………………………………………. pp. 66 – 68

Diencephalon (Hypothalamus) …………………………………………pp. 69 – 74

Limbic System …….……………………………………………………… pp. 75 – 81

Visual System …………………………………………………………….. pp. 82 – 86

Cortex & Review …………………………………………………………. pp. 87 – 92

Labeled Slides from Slide Set …………………………………………. pp. 93 – 110



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INTRODUCTION

The purpose of this syllabus is to assist and guide the student through the

neuroanatomy laboratory portion of Medical Neuroscience (MEID 936) in a systematic

fashion. It has been prepared specifically for the curriculum at the Texas A&MUniversity Health Science Center College of Medicine. The ultimate goal of the

laboratory portion of this course is to provide a "hands on" experience in learning and

understanding the FUNCTIONAL anatomy of the human central nervous system (CNS).

To assist you in this endeavor, this syllabus will be used in conjunction with the

following laboratory materials:

1. The Medical Neuroscience Laboratory Manual (downloaded from

Blackboard9 (https://elearning.tamhsc.edu/) under MEID 936 Neuroscience

Phase II. This file contains the Neuroscience Manual & Slide Set.

2. Two brain buckets (shared by a MDL group) containing:

#: Whole and Half Brain

#A: Horizontally and Coronally Sectioned Brains

3. An atlas of Neuroanatomy. Each laboratory group will receive one copy of

the Atlas of the Human Brain and Spinal Cord (Fix, J., 2nd ed.). It is

strongly recommended that your laboratory group use your atlas in eachlaboratory session. Moreover, it will be of value in all phases of this course to

help you in understanding the 3 - dimensional anatomy of the human nervous

system.

There is also an additional item that the student should download from

Blackboard9. This includes a set of annotated Neuroscience slides (Neuroscience Lab

Manual Supplement). The file of labeled slides contains representative spinal cord and

brainstem sections taken from your slide set.

https://elearning.tamhsc.edu/





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NOTE: UNDER NO CIRCUMSTANCES ARE THE BRAIN SPECIMENS TO BE

REMOVED FROM THE LABORATORY AT ANY TIME.

To assist you in learning the neuroanatomical structures discussed in this

laboratory syllabus, there is an “Objectives” statement at the beginning of each

laboratory section. Further, the important structures and/or concepts for each

laboratory are in bold print or are underlined. In addition, questions pertinent to the

area being studied are interspersed throughout each laboratory session in italicized

print .

Laboratory Demonstrations -- Typically, there will be laboratory demonstrations

during each laboratory session. These will consist of models and/or pre-dissected wet

specimens. Since these demonstrations will be "fair game" for laboratory practicalexams, it is recommended that you take the time to view them when they are displayed

during normal laboratory hours.

Finally, it will be useful to read through each laboratory assignment, using your

brain atlas, prior to the laboratory session. This should help make both lecture and

laboratory material easier to comprehend.



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GROSS ANATOMY OF THE BRAIN

Objectives: 1. Understand the directional terminology of the CNS.

2. Learn the names and locations of the gross anatomical structures of

the brain.

Before we begin, it is important to understand the directional terminology or

nomenclature as it relates to the brain. Below is a diagram (Fig. 1) to assist you in

understanding this terminology. It is important that you understand it, since we will be

using this terminology in lecture and laboratory throughout the course to describe the

relative locations of various CNS structures.

In this laboratory session, we will be studying what could be called "lump and

bump" anatomy. That is, we will be identifying and briefly discussing the gross externaland internal anatomy of the brain. The purpose of this laboratory is simply to

acquaint you with the appearance and location of structures that we will be

revisiting in detail as the course progresses. These structures will also be used

as landmarks to locate and identify other anatomical features of the brain. Use



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your atlas to assist in the identification of the structures listed in this and all

future laboratory sessions.

Whole and Half Brain Specimens

We will begin by identifying the features of the major subdivisions of the brain,

using the whole and half brain specimens in your brain buckets. The brain is organized

from rostral to caudal as follows: 1) telencephalon, 2) diencephalon, 3) mesencephalon

[midbrain], 4) metencephalon [pons], 5) myelencephalon [medulla oblongata] and 6)

cerebellum. Items 2 through 5 above are collectively called the brainstem.

The telencephalon is composed of the cerebral hemispheres and portions of the

basal ganglia. The latter will be studied in a subsequent laboratory session. Thecerebral hemispheres are the large, external, convoluted mantles of nervous tissue

that overlie the brainstem. The superficial region of the cerebral hemispheres is

composed of gray matter. Immediately deep to the gray matter is a relatively thick

layer of white matter. To confirm this, look at selected horizontal and coronal sections.

How does this compare to what is seen in spinal cord? The cerebral hemispheres are

divided into right and left halves at the midline by the prominent interhemispheric

(longitudinal cerebral) fissure. The raised areas, or convolutions, on the surface of

the cerebral hemispheres are called gyri (sing. - gyrus). The corresponding grooves

or depressions are collectively called sulci (sing. - sulcus). The larger, deeper

grooves are usually referred to as fissures.

Each cerebral hemisphere is divided into lobes (Fig. 2). Observe the brain from

a lateral view. From this perspective, it resembles a catcher's mitt with the "thumb"

portion located in a ventrolateral position. This "thumb" portion is the temporal lobe. It

is separated from the more dorsal aspect of the brain by a deep groove called the

lateral (Sylvian) fissure. Locate the horizontally arranged superior, middle and

inferior temporal gyri. The middle temporal gyrus is separated from the superior and

inferior temporal gyri by the superior and middle temporal sulci. Immediately dorsalto the lateral fissure is the frontal lobe, which extends from the rostral pole (end) of the

brain caudally to the central sulcus (of Rolando). This sulcus separates the frontal

lobe from the parietal lobe. Two important gyri lie immediately rostral (precentral

gyrus) and caudal (postcentral gyrus) to the central sulcus. Immediately rostral to the

precentral gyrus is the precentral sulcus. Rostral to the precentral sulcus lie three



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horizontally arranged gyri. These are, from dorsal to ventral, the superior, middle and

inferior frontal gyri. The middle frontal gyrus is separated from the superior and

inferior frontal gyri by the superior and inferior frontal sulci.

The caudal extent of the parietal and temporal lobes is delineated by an

imaginary line drawn from the parietooccipital sulcus dorsally to the preoccipital

notch ventrally (Fig. 2). The remaining region of brain from the "imaginary line"

caudally is called the occipital lobe. The caudalmost extent of the occipital lobe is

called the occipital pole. The parietal lobe is separated from the temporal lobe by

drawing an imaginary horizontal line that extends caudally from the Sylvian fissure to

the previous "imaginary line" between the parietooccipital sulcus to the preoccipital

notch.

The caudal end of the Sylvian fissure turns dorsally to terminate and is

surrounded by the supramarginal gyrus. Deep to the Sylvian fissure lies a region of

cortex called the insula (insular lobe). Identify this structure on your horizontal andcoronal brain slices. In some instances, the insula can be seen on the whole or half

brain by GENTLY separating the frontal and temporal lobes. If you are unable to see

the insula on your whole or half brain specimens, this structure can be seen clearly on

demonstration. DO NOT FORCE THE LOBES APART BY TEARING BRAIN TISSUE.



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Now turn the whole brain over to view the ventral surface. Beginning on the

lateral aspect of the temporal lobe and working medially, find the inferior temporal

sulcus, occipitotemporal (fusiform) gyrus, collateral sulcus and parahippocampal

gyrus. Near the rostral end of the parahippocampal gyrus is a small, medially directed

protuberance of cortical tissue called the uncus.

To complete our survey of the cerebral hemispheres, observe the medial surface

of the half brain. Find the central sulcus as it winds its way onto the dorsal aspect of

the medial surface of the cerebral cortex to terminate. Surrounding the termination of

the central sulcus is the paracentral lobule, which is a fusion of pre- and postcentral

gyri. Immediately caudal to the paracentral lobule is a region of cortex called the

precuneus. It is bounded caudally by the vertically oriented parietooccipital sulcus.

From the occipital pole, the calcarine sulcus runs rostrally to join the parietooccipital

sulcus. The calcarine sulcus divides the occipital lobe into a dorsal region called thecuneus and a ventral region called the lingula.

Located at the approximate center of the medial surface of the half brain is a

sickle shaped structure, the corpus callosum. This is a massive interhemispheric

nerve fiber pathway that provides reciprocal communication between the two cerebral

hemispheres. It is divided into parts from rostral to caudal as follows: rostrum, genu,

body and splenium. The corpus callosum is surrounded by cerebral cortex that

contributes to a structure we will study in detail later called the limbic lobe. From

rostral to caudal, the visible structures of the limbic lobe include the subcallosal gyrus

(located immediately ventral to the rostrum of the corpus callosum), the cingulate

gyrus (surrounding the dorsal aspect of the corpus callosum), the isthmus of the

cingulate gyrus (located immediately ventral to the splenium of the corpus callosum)

and the parahippocampal gyrus of the temporal lobe. The limbic lobe also includes

the hippocampal formation and dentate gyrus (hidden from view within the temporal

lobe). These latter structures will be seen in a subsequent laboratory. Immediately

dorsal to the cingulate gyrus, find the cingulate sulcus.

Hanging from the ventral surface of the corpus callosum is a membrane called

the septum pellucidum. Along the free ventral border of the septum pellucidum is afiber bundle called the fornix. Follow the fornix as it arches rostrally. In the region just

rostral to where the fornix dives out of site is a small interhemispheric fiber bundle called

the anterior commissure. This structure interconnects portions of the temporal lobes

and components of the olfactory system. Immediately rostral and ventral to the anterior

commissure is a thin membrane called the lamina terminalis. This structure spans the



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midline. As such, it has been cut on your half brain specimens. The closure of what

embryological structure gives rise to the lamina terminalis? Follow the lamina terminalis

ventrally to the optic chiasm. Note that the optic chiasm is continuous with the optic

nerves rostrally and the optic tracts caudally. Just caudal to the optic chiasm is the

infundibulum (pituitary stalk). Arching caudally from this structure is another thin

sheet of tissue called the tuber cinereum, which leads to the paired mammillary

bodies. (NOTE: since you are viewing the half brain, there will be only one mammillary

body). The region of brain roughly between the lamina terminalis and the caudal aspect

of the mammillary bodies is the hypothalamus. It is separated from the dorsally

located, egg-shaped thalamus by a rostrocaudal groove called the hypothalamic

sulcus. Running along the dorsomedial aspect of the thalamus is a threadlike elevation

of tissue called the stria medullaris thalami. At the caudal end of this structure are the

habenula, pineal gland and posterior commissure.On the half brain, the medial surface of the thalamus typically reveals a severed

medial protrusion of thalamic tissue. This is the remnants of the massa intermedia

(interthalamic adhesion) which, when present, connects the left and right thalami.

The hypothalamus, thalamus, habenula and pineal gland constitute the major portion of

the diencephalon, the most rostral extent of the brainstem. Another structure, the

subthalamus, is also a part of the diencephalon and will be seen at a later date. It

should be noted at this point that there is a space between diencephalic structures on

the left and right sides. This centrally located space is the third ventricle.

At the juncture of the thalamus and midbrain (mesencephalon), there is a

ventral flexure of the brainstem. This is called the cephalic flexure. Proceeding

caudally (inferiorly) from the mammillary body on the half brain, there is a relatively

deep longitudinal furrow in the midline. This is the interpeduncular fossa. Just lateral

to the interpeduncular fossa, observe one of the paired cerebral peduncles (crus

cerebri). These are important structures that carry descending nerve fibers from the

cerebral cortex to other regions of the brain and spinal cord. If intact, the oculomotor

nerve (CN III) can be seen emerging from the medial surface of the cerebral peduncle.

On the dorsal surface of the midbrain immediately caudal to the posterior commissurelie two rounded protuberances. The more rostral one is the superior colliculus, which

is associated with the visual system. The more caudal one is the inferior colliculus,

which is associated with the auditory system. On the whole brain, each of these colliculi

are paired structures (i.e., two superior colliculi, two inferior colliculi [see demonstration])

and are collectively referred to as the corpora quadrigemina or tectum of the



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midbrain. Separating the tectum and the more ventrally located tegmentum of the

midbrain is a small rostro-caudal channel called the cerebral aqueduct (of Sylvius).

The large ventral convexity caudal to the cerebral peduncles is the pons

(metencephalon). If an imaginary line is drawn from the inferior aspect of the inferior

colliculus ventrally to the junction of the cerebral peduncles with the pons, this roughly

represents the caudal extent of the midbrain. Follow the pons dorsolaterally. Just

caudal to where the trigeminal nerve (CN V) emerges, there is a thick band of nerve

fibers connecting the pons with the overlying cerebellum. This is the middle

cerebellar peduncle (brachium pontis). (NOTE: there are also inferior and

superior cerebellar peduncles that can be seen on demonstration). The "potbellied"

pons ends caudally where it meets the medulla (myelencephalon) at the medullary-

pontine junction. This can be seen as a horizontal groove from which the abducens

(CN VI), facial (CN VII) and vestibulocochlear (CN VIII) nerves emerge from medialto lateral respectively. The lateral-most portion of this groove where CN VII and VIII

emerge is called the cerebellopontine angle. This is where the pons, medulla and

cerebellum join together. The large cerebellum can be seen sitting astride the dorsal

surfaces of the pons and medulla. Two thin sloping membranes (superior & inferior

medullary vellae) usually can be seen stretching between the cerebellum and the

dorsal surface of the brainstem. The more rostral is the superior medullary velum.

The inferior medullary velum is often difficult to see. This structure stretches from the

inferior aspect of the cerebellum to the medulla. Both vellae form a triangular space

with the pons and medulla, called the fourth ventricle.

The ventral surface of the medulla is best seen on the whole brain. On either

side of the midline on the medulla just caudal to the medullary-pontine junction is a pair

of rounded ridges. These are the pyramids and are caused by the underlying

pyramidal (corticospinal) tract. Immediately lateral to the pyramids at this level are a

pair of egg-shaped swellings called the inferior olives. The inferior olivary nuclei

reside deep to these structures. The groove between the inferior olive and the pyramid

on each side is the preolivary sulcus. Filaments of the hypoglossal nerve (CN XII)

can be seen emerging from this sulcus. Dorsolateral to the inferior olive is anothergroove called the postolivary sulcus from which the glossopharyngeal (CN IX),

vagus (CN X) and the bulbar portion of the spinal accessory (CN XI) nerves

emerge.

Identify the following structures on the whole brain: lamina terminalis, optic

nerves, optic chiasm, optic tracts, infundibulum, tuber cinereum, mammillary



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bodies, cerebral peduncles, interpeduncular fossa, CN III, pons, CN V, VI, VII and

VIII, middle cerebellar peduncle.

DEMONSTRATIONS

Dorsal brainstem showing: thalamus, pineal gland, superior and inferior

colliculi, brachia of superior and inferior colliculi, trochlear nerve (CN IV),

superior, middle and inferior cerebellar peduncles, tuberculum gracilis,

tuberculum cuneatus, fourth ventricle. Use Fig. 3 below to assist in

identifying the above structures on the demonstration.

Half brain (lateral view) showing: central sulcus, lateral fissure, precentral and

postcentral gyri, insula, paracentral lobule, angular gyrus, supramarginal

gyrus.



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Half brain (medial view) showing: paracentral lobule, parietooccipital sulcus,

calcarine sulcus, lingula, cuneus, corpus callosum (all parts), cingulate

gyrus.

NOTES



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MENINGES

Objectives: 1. Review the layers of the meninges as learned in Gross Anatomy.

2. Locate and be able to name the subarachnoid cisterns which surround

the brain and spinal cord.

The meninges consist of 3 concentric membranous layers of tissue that surround the

brain and spinal cord.

Dura mater -- The outermost, thick, fibrous layer of meninges is called the dura

mater. As many of you know from gross anatomy, the dura mater is made up of 2

layers (an inner [meningeal] and outer [endosteal/periosteal] layer) that are typically

fused together. The outer layer is, in turn, fused to the inner surface of the skull. Assuch, there will not be any dura mater on the brains in your buckets. It should be noted

that the periosteal layer of dura mater passes through the foramen magnum to fuse with

the periostium on the external surface of the skull. Consequently, the only layer of dura

mater covering the spinal cord is the meningeal layer. Since the dura mater is

intimately involved in the drainage of blood from the brain, there will be a demonstration

of the dura mater and its reflections within the skull later in this laboratory session

during our review of the blood supply to the CNS.

Arachnoid mater -- This intermediate layer of the meninges usually remains at

least partially intact on the surface of the brain after it is removed from the skull. On the

whole or half brain, look on the lateral surfaces of the cerebral hemispheres. If the

arachnoid mater is present, it will appear as a transparent membrane that spans the

sulci and fissures of the cerebral cortex. Immediately deep to the arachnoid mater lies

an important region called the subarachnoid space. It contains: 1) cerebrospinal fluid

and 2) the major blood vessels of the brain. Using a blunt probe, slip the tip through an

existing gap or tear in the arachnoid mater and gently elevate the arachnoid layer to

demonstrate the subarachnoid space. Over most of the surface of the brain, thesubarachnoid space is relatively shallow. However, in those regions where there are

wide and/or deep depressions on the surface of the brain, the arachnoid layer stretches

across these depressions, resulting in enlargement of the subarachnoid space. These

enlargements are called subarachnoid cisterns.



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Using both the whole and half brains, four of the major cisterns can be

demonstrated. On the ventral surface of the midbrain, locate the cerebral peduncles.

The depression in the midline between the cerebral peduncles is the interpeduncular

fossa. If the arachnoid is present, it will be seen stretching across the interpeduncular

fossa between the cerebral peduncles. The space formed between the floor of the

fossa and the overlying arachnoid layer is called the interpeduncular cistern.

Immediately caudal to the cerebral peduncles lies the convex protuberance of the

ventral pons. The pontine cistern lies immediately ventral to the pons and extends

caudally to enlarge and terminate at the junction of the pons and medulla (medullary-

pontine junction). Now turn the brains over to view the dorsal surface. The two

cisterns on this surface of the brain lie either immediately rostral or caudal to the

cerebellum. The more rostral of these, the superior cerebellar (quadrigeminal)

cistern is best seen on the medial surface of the half brain. It is roughly bounded bythe splenium of the corpus callosum superiorly, the superior and inferior colliculi

(corpora quadrigemina) ventrally and the superior surface of the cerebellum inferiorly.

The remaining cistern of note, the cerebellomedullary cistern (cisterna magna), lies

at the inferior surface of the cerebellum and the dorsal surface of the medulla where the

arachnoid layer reflects from the cerebellum to the medulla. Use your blunt probe to

gently explore the extent of these cisterns. It is important to note that another clinically

important cistern is located immediately caudal to the termination of the spinal cord.

What is the name of this cistern? At what vertebral level does the spinal cord

terminate?

Pia mater -- This innermost layer of the meninges is, for the most part, closely

adhered to the surface of the brain and spinal cord. As such, it is difficult to

demonstrate with the naked eye. At the microscopic level, small blood vessels that

penetrate the parenchyma (substance) of the brain are surrounded by pial sleeves that

penetrate variable distances into the brain. There are two obvious occasions where the

pia mater separates from the surface of the CNS and can be readily seen. What is the

site of each of these pial separations and what they are called? (Think Gross Anatomy).

NOTES



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BLOOD SUPPLY TO THE BRAIN AND SPINAL CORD

Objectives: 1. Learn the major arteries of the CNS and the areas they supply.

2. Review the dural venous sinuses and learn the major veins that drain

the CNS.

Vascular injury and/or vascular disease constitute a major source of nervous

system pathology. The CNS is critically dependent upon glucose and oxygen, neither of

which is stored in significant amounts by the CNS. Consequently, should the blood

supply to the CNS be disrupted, even for a relatively brief period, destruction of CNS

parenchyma occurs with the resultant permanent loss of function, or death.

Brain -- The blood supply to the brain is typically described as being provided bytwo arterial systems: an anterior system which is composed of the internal carotid

arteries and their branches; and the posterior (vertebral - basilar) system, composed of

the vertebral arteries. These two systems are demonstrated in Fig. 4 below.



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Posterior System -- Using the whole brain, turn it over to view the ventral

surface. Note the paired vertebral arteries ascending on the ventrolateral surface of

the medulla. As you may recall, the vertebral arteries arise from the subclavian arteries

and ascend through the foramina transversaria of cervical vertebrae C-6 through C-1 to

enter the skull through the foramen magnum. Typically, the vertebral arteries fuse at

the midline at the level of the medullary-pontine junction to form the unpaired basilar

artery. Before the vertebral arteries fuse, they give rise to three pairs of arteries. The

first of these are the posterior spinal arteries that descend on the dorsal surface of the

spinal cord just medial to the dorsal spinal roots. Since the posterior spinal arteries are

typically the first to arise from the vertebral arteries as they traverse the foramen

magnum, they are often absent due to the level where the vertebral arteries were cut

when the brain was removed from the skull. The second branches are the posterior

inferior cerebellar arteries (PICA) which wrap around the medulla to ramify on theinferior surface of the cerebellum. As these arteries wrap around the medulla to gain

access to the cerebellum, they send small branches to supply the lateral region of the

medulla. Occasionally, the posterior spinal arteries may arise from PICA. The anterior

spinal arteries, which descend to fuse as a single artery at the midline on the ventral

surface of the medulla, are usually the last branches from the vertebral arteries before

they fuse to become the basilar artery. Shortly after the basilar artery is formed, it

gives rise to the paired anterior inferior cerebellar arteries (AICA), which ramify on

the ventral surface of the cerebellum. Immediately rostral to these arteries, the basilar

artery gives rise to the paired labyrinthine (internal auditory) arteries each of which

follow their respective vestibulocochlear nerve (CN VIII) into the internal auditory

meatus. Often, these arteries arise from AICA rather than the basilar artery. As the

basilar artery ascends on the ventral surface of the pons, it gives rise to many small

pontine arteries. Just prior to terminating, the basilar artery gives rise to the paired

superior cerebellar arteries, which wrap around and supply the midbrain on their way

to ramify on the superior surface of the cerebellum. The basilar artery terminates at the

level of the midbrain by dividing into the large, paired posterior cerebral arteries. At

this time, look for the oculomotor nerve (CN III) which acts as a landmark by emergingbetween the posterior cerebral and superior cerebellar arteries.

Anterior System -- After entering the skull through the carotid canal, each

internal carotid artery passes through the cavernous sinus, then turns 180°

caudalward to gain access to the ventral surface of the brain. It is at this point that the



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internal carotid arteries are cut to remove the brain from the skull. On the ventral

surface of the whole brain, find the severed ends of the internal carotid arteries as

they lie just lateral to the optic chiasm. There are four branches that can be readily

seen arising from the internal carotid arteries: two from the main trunk and two terminal

branches. The first small branch is the posterior communicating artery. This artery

passes caudally to anastomose with the posterior cerebral artery. The next branch is

the anterior choroidal artery. This small artery passes caudally to disappear deep to

the temporal lobe. As the name implies, this artery supplies blood to the choroid

plexus (and other structures). Shortly after the internal carotid artery gives rise to the

anterior choroidal artery, it divides into its two terminal branches, the anterior and

middle cerebral arteries. The latter is larger and considered by some to be the

continuation of the internal carotid artery. Immediately distal to the origin of the anterior

choroidal artery, a variable number (2-5) of small threadlike arteries can be seen arisingfrom the middle cerebral artery and immediately diving into brain parenchyma. These

are the lateral striate (lenticulostriate) arteries. Although small, these arteries supply

critical areas of the brain. The middle cerebral artery continues laterally to dive into the

lateral sulcus (Sylvian fissure) deep to the rostral pole of the temporal lobe.

Branches of the middle cerebral artery can be seen on the lateral surface of the brain as

they emerge from the lateral sulcus.

On the ventral surface of the whole brain, the anterior cerebral arteries can be

seen coursing medially to pass dorsal (deep) to the optic nerves. As they approach the

midline just rostral to the optic chiasm, these arteries are joined together by an

anastomotic channel called the anterior communicating artery. Both anterior cerebral

arteries then disappear by diving into the interhemispheric fissure, each one

supplying ipsilateral structures on the medial and dorsal surface of the brain.

On your half brains, follow the course of an anterior cerebral artery as it

courses along the rostral and dorsal surfaces of the genu of the corpus callosum. At

this point, the anterior cerebral artery typically divides into its two terminal branches, the

pericallosal and callosomarginal arteries. The pericallosal artery runs caudally

along the dorsal surface of the body of the corpus callosum. The callosomarginalartery takes a more dorsal path caudally by running in or near the cingulate sulcus.

Note the branches of these arteries and the general areas they supply.

Now turn your attention back to the ventral surface of the whole brain. The

posterior cerebrals, posterior communicating, internal carotids, anterior cerebrals

and anterior communicating arteries form an arterial circle (of Willis) at the base of



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the brain surrounding the hypothalamus, infundibulum and optic chiasm. Notice the

many small arteries arising from the internal surfaces of the circle of Willis. They are

generally referred to as central or ganglionic arteries. The circle of Willis is clinically

important in that if a blood vessel should be occluded on one side of the circle, blood

can be shunted to bypass the obstruction. However, since this arterial circle is variable,

i.e. branches small or missing, this is not an iron clad rule.

Another issue to consider is that although there is some overlap along the

periphery of the territory for adjacent arteries supplying the brain, these arteries are

functionally "end" arteries, in that they are the sole blood supply to the vast majority of a

given area of brain. Consequently, permanent or prolonged occlusion of a single artery

results in necrosis of the brain area supplied by that artery.

Venous Return -- Unlike the arterial supply to the brain, venules emerge fromthe substance of the brain as fine pial plexuses that coalesce to form larger visible veins

that reside in the subarachnoid space. A good example of this can be seen on the

surface of the cerebral hemispheres. An exception to this general rule can be seen on

the medial surface of a half brain. Look along the dorsomedial aspect of the thalamus

on a half brain. A relatively large vein can usually be seen running in a rostrocaudal

direction. This vein drains deeper brain structures and is called the internal cerebral

vein. As this vein reaches the subarachnoid space at the caudal aspect of the

thalamus, you may be able to see another vein joining the internal cerebral vein from

the ventral side. This is the basal vein (of Rosenthal). If you do not have this vein on

your specimen, it can be seen on demonstration. After it is joined by the basal vein, the

internal cerebral vein becomes the great cerebral vein (of Galen). Into what venous

structure does the great cerebral vein empty? What is the name of the subarachnoid

compartment where the above veins join together?

Although the larger veins within the subarachnoid space on the surface of the

brain generally run in parallel with their arterial counterparts, these veins soon depart

from the arteries to drain into specialized endothelium-lined venous channels between

the meningeal and periosteal layers of the dura mater called dural venous sinuses. These sinuses are formed in certain regions of the cranial cavity where the inner

(meningeal) layer of dura mater separates from the outer (periosteal) layer to form: 1)

horizontal septae that divide the cranial cavity into compartments, or 2) vertical septae

that occupy the fissures between the left and right cerebral and cerebellar hemispheres.



19

Using any gross anatomy text or atlas, identify and note the location of the

following dural septae and major dural venous sinuses: falx cerebri, superior sagittal

sinus, inferior sagittal sinus, tentorium cerebelli, tentorial notch (incisure),

straight sinus, confluence of sinuses, transverse sinus, sigmoid sinus and

cavernous sinus. What subdivision of the brainstem occupies the region within the

tentorial notch? At this time, you should review the direction of normal blood flow in

these dural venous sinuses. What major vein receives blood from the sigmoid sinus?

Spinal Cord -- The spinal cord has a longitudinal and segmental blood supply.

The longitudinal supply is provided by the anterior (one) and posterior (two) spinal

arteries arising from the vertebral arteries. However, these small arteries alone are

only sufficient to supply upper cervical segments. Consequently, the primary source of

spinal cord blood supply is provided by segmental arteries at cervical, thoracic andupper lumbar levels of the vertebral column. These arteries gain access to the spinal

cord through intervertebral foramina where they reinforce the longitudinal supply

through anastomotic channels.

The spinal branches of the segmental arteries enter the intervertebral foramina

and then divide and ramify along the dorsal and ventral spinal roots to reinforce the

longitudinal blood supply to the spinal cord. Spinal veins generally follow their arterial

counterparts on the surface of the spinal cord. However, these veins drain into the

internal vertebral venous plexus, which in turn has connections with the external

vertebral venous plexus and segmental veins. Do these venous plexuses have valves?

What other venous plexuses interconnect with the vertebral venous plexuses?

DEMONSTRATIONS

Skull showing dural reflections and venous channels: falx cerebri, superior

sagittal sinus, inferior sagittal sinus, tentorium cerebelli, tentorial notch

(incisure), straight sinus, confluence of sinuses, transverse sinus.

Ventral surface of whole brain showing blood supply: Identify blood vessels as

labeled in Fig. 4 (p. 15) of this laboratory exercise.

NOTES



20

CSF AND VENTRICLES OF THE BRAIN

Objectives: 1. Identify and locate all parts the ventricular system of the brain.

2. Identify the brain structures that form the walls/boundaries of the

various parts of the ventricular system.

3. Understand the normal flow of CSF through the ventricles and the

general consequences of ventricular system blockage.

The brain is not a solid mass of nervous tissue. There are four interconnected

cavities, called ventricles, deep within the brain. The two lateral ventricles are located

within the cerebral hemispheres. The third ventricle is situated in the midline between

the left and right portions of the thalamus and hypothalamus. The fourth ventricle is

located between the cerebellum dorsally, and the pons and medulla ventrally. Eachventricle contains structures called choroid plexuses, which produce cerebrospinal fluid

(CSF). The normal flow of CSF within the ventricular system is as follows:

lateral→third→fourth. After it flows through the ventricles, it then gains access to the

subarachnoid space through small foramina in the fourth ventricle. The CSF then

percolates throughout the subarachnoid space surrounding the brain and spinal cord to

eventually empty into the venous system. In addition to supporting and protecting the

brain, CSF is important in the metabolic processes of the brain. The CSF also serves

as an important diagnostic tool for a variety of neurological problems, and can be

aspirated for analysis. It is critical that the CSF has unobstructed flow through the

ventricular system of the brain and into the subarachnoid space. If blockage should

occur, there will be a subsequent expansion of "upstream" ventricles (hydrocephalus),

causing compression of surrounding brain tissue.

Half Brain; Horizontal and Coronal Sections

Observe the medial surface of your half brain specimen. Find the thalamus and

hypothalamus. The area between (medial to) these structures and their contralateralcounterparts is the third ventricle. Find the anterior commissure and the rostral

pole of the thalamus. Between these structures is a small hole called the

interventricular foramen (of Monro). There are two of these foramina, one on each

side. They interconnect the lateral ventricles with the third ventricle. If present, the

choroid plexus can be seen hanging from the roof of the third ventricle. At the caudal



21

end of the thalamus, the third ventricle narrows into a small passageway, the cerebral

aqueduct (of Sylvius), which courses through the midbrain to open into the fourth

ventricle. The fourth ventricle is continuous caudally with the central canal of the spinal

cord. Attempt to find the choroid plexus in the fourth ventricle. It is from the fourth

ventricle that the CSF enters the subarachnoid space. It does so by passing through: 1)

a single midline foramen (foramen of Magendie) located at the caudal extent of the

fourth ventricle where the inferior medullary velum contacts the medulla, and 2) two

lateral foramina (foramina of Luschka) located at the lateral extremes of the fourth

ventricle. The foramina of Luschka can be found by GENTLY insinuating the tip of your

blunt probe into the lateral reaches of the fourth ventricle. If you have done this

correctly, the tip of the probe will pass through the foramen of Luschka to appear

externally in the cerebellopontine angle. It is common for the choroid plexus of the

fourth ventricle to extend through the foramina of Luschka to reside in the subarachnoidspace. Look in the region of the cerebellopontine angle for tufts of this structure as it

emerges.

The lateral ventricles are located in the cerebral hemispheres. They can be

viewed in their entirety by using both horizontal and coronal brain slices. Using your

brain atlas, begin at the dorsal aspect of the horizontally sliced brain and remove slices,

observing both surfaces of each slice, until the lateral ventricles are exposed. Note that

the fibers of the corpus callosum form the roof, as well as the anterior and posterior

boundaries of the lateral ventricles. Identify the genu, body and splenium of the

corpus callosum. Find the choroid plexus within the lumen of the lateral ventricles

and third ventricle. Identify the frontal (anterior) horn, body and occipital (posterior)

horn of the lateral ventricles. Note the rounded mass that forms the lateral boundary

of the frontal horns. This is the head of the caudate nucleus, a component of the

basal ganglia. Find the thalamus, septum pellucidum and fornix, and determine their

spatial relationships to the lateral ventricles. As you progress from dorsal to ventral,

there is a region near the caudal end of the lateral ventricles where the body, occipital

horn and temporal (inferior) horn meet. This is called the trigone (atrium) of the

lateral ventricle. Follow subsequent sections ventrally into the temporal horn.Find a horizontal section similar to that in the Fix Atlas: Plate 56 (p. 112) and

identify the interventricular foramina (of Monro). As previously stated, these two

foramina are the openings from the lateral ventricles into the centrally located third

ventricle. Just lateral to each of these foramina is a "V" shaped region of white matter

called the internal capsule, an important bidirectional pathway between the cortex and



22

the brainstem and spinal cord. The apex of each "V" is called the genu of the internal

capsule. Each genu is directed medially and points at the interventricular foramen on

each side, thus serving as a landmark. The genu is continuous with the anterior and

posterior limbs of the internal capsule.

Using your coronal brain slices and your brain atlas, identify the same

structures you found in the horizontal sections. Compare and contrast these

structures as they appear in horizontal and coronal section. The purpose of this

important exercise is to begin to appreciate and understand the three dimensional

anatomy of the brain, which is critical if you are to be successful in this course.

NEURORADIOLOGY

You should now have a basic understanding of the gross anatomy of the brain. Ifthis assumption is correct, you should have little difficulty transferring this knowledge to

interpret the variety of radiologic techniques that are used to visualize the various parts

of the brain.

Using your Neuroscience slide set, look at slide 45. This is a mid-sagittal section

of the brain as visualized by magnetic resonance imaging (MRI). This particular MRI is

a T1 weighted image. What are the visual characteristics of a T1 weighted MRI of the

brain such as the one seen on this slide? Identify the following brain structures/regions

on this slide with the help of your half brain specimens: corpus callosum (all

portions), cingulate gyrus, fornix, thalamus, cerebral aqueduct (note arrowheads),

subarachnoid cisterns (interpeduncular, pontine, superior cerebellar, cisterna

magna), parietooccipital sulcus, calcarine fissure, cuneus, lingula, cerebellum,

fourth ventricle, medulla, pons, midbrain, superior and inferior colliculi,

mammillary body, hypothalamus, optic chiasm, optic nerve and interventricular

foramen of Monro.

Slide 46 is an MRI (T1 weighted) of the brain in coronal section. Using a similar

coronal slice from your brain specimens as an aid, identify the lateral ventricles, third

ventricle, thalamus, body of the corpus callosum, lateral fissure, insula, temporallobe and interhemispheric fissure.

Slide 47 is a T1 weighted MRI taken in the horizontal plane. Using a similar

horizontal slice from your brain specimens as an aid, identify the frontal horns of the

lateral ventricles, third ventricle, head of the caudate, thalamus, internal capsule

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23

(all parts), trigone (atrium) of lateral ventricle, splenium of corpus callosum,

lateral fissure and insula.

Slide 51 shows two T2 weighted horizontal images of the brain. In the left

image, note the occipital horn of the lateral ventricle on the left side of the slide. Is

this the patient’s left side? Which of the two images is higher (more superior)? The

midbrain and the middle and posterior cerebral arteries can also be seen. Note the

location and orientation of the cerebral peduncles. Verify this by comparing this image

with a similar horizontal section from your brain specimens. The right image shows the

frontal horns of the lateral ventricles, third ventricle, and trigone (atrium) of the

lateral ventricles. How does the appearance of the ventricles on this slide differ from

that seen in a T1 weighted image? Slide 65 is a similar MRI, showing anterior, middle

and posterior cerebral arteries as well as mammillary bodies, third ventricle,

rostral midbrain and uncus. Is this a T1 or T2 weighted image? Look at slide 64. Is this section rostral or caudal to slide 65 ? What blood vessels can be seen in this view?

DEMONSTRATIONS

Cast of actual human ventricular system.

NOTES

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24

INTRODUCTION TO THE MACROSCOPIC ANATOMY OF THE NEURAXIS

Objective: 1. Be able to quickly identify representative levels of the neuraxis,

including the salient internal and external features of these

representative levels as viewed on the stained, macroscopic sections

in your slide sets.

As part of the learning aids in the neuroanatomy laboratory, you have been

provided with a set of slides showing the macroscopic anatomy of the human brain and

spinal cord. The slides are arranged in ascending order, beginning with the sacral

spinal cord (slide #1) and ending with telencephalic structures. Those sections of

the neuraxis from spinal cord through midbrain are cut in horizontal section. Because of

the flexure of the brain between the diencephalon and midbrain, subsequent slidesshow brain sections cut in varying planes between horizontal and coronal. The purpose

of the following exercise is to familiarize you with the "typical" appearance of the various

levels of the spinal cord and brainstem so that you can instantly recognize these levels

when you see them. Make extensive use of your brain atlas, and the supplementary

labeled slides (available on Bb9 and at the back of this laboratory syllabus), to assist

you in the identification of internal and external landmarks at these various levels.

Spinal Cord (slides 1-5)

Observe slide 1. This is a cross section of the sacral spinal cord. The dorsal

surface of this section, as well as subsequent sections of spinal cord and brainstem

through the midbrain, is located at the top of the slide. The vast majority of the sections

on the slides are stained with one of two types of nerve fiber stains. Slide 1 is stained

by the luxol fast blue method for myelinated nerve fibers, and counterstained with

hematoxylin and eosin to reveal neuronal cell bodies. Note the dark blue staining of the

white matter (nerve fibers) around the periphery, and the relative absence of blue

staining in the centrally located gray matter, which contains neuronal cell bodies. Thebutterfly shaped gray matter is divided into dorsal (posterior) and ventral (anterior)

horns with an intervening lateral horn. The latter will be seen more clearly in

subsequent sections. Note the gray commissure that connects the left and right sides

of the gray matter. Observe the small purple dots scattered throughout the ventral horn.

These are the ventral motor horn cells that give rise to the majority of axons within the

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25

ventral roots. Observe the arched pink region near the top of the dorsal horn. This is

the substantia gelatinosa, an important sensory relay nucleus. The gray matter

immediately ventral to the substantia gelatinosa contains the less distinct nucleus

proprius (proper sensory nucleus). The white matter dorsal to the substantia

gelatinosa is Lissaur's tract, an intersegmental spinal pathway. The white matter can

be roughly divided into funiculi (columns) based on their position in the spinal cord.

The dorsal funiculus is located between the dorsal horns of the gray matter. The

lateral funiculus occupies the region between the dorsal and ventral roots. The

ventral funiculus lies between the midline and the emergence of the ventral roots.

Immediately ventral to the gray commissure is the anterior white commissure, which

contains nerve fibers that cross the midline. The prominent dorsal and ventral median

fissures serve to vertically divide the white matter at the midline. Each of the above

funiculi contain important ascending and descending nerve fiber tracts that will beidentified at a later date. Note the single anterior spinal artery and the multiple

posterior spinal arteries and their location immediately external to the pia mater.

Now look at slide 2. This is a cross section of the lower lumbar spinal cord

stained with the Weil stain. This histological procedure stains the myelin of nerve fibers

black. The gray matter (cell bodies) remains unstained with the exception of those

regions where myelinated nerve fibers traverse it. Observe the large lateral projections

of the ventral horns. What is the purpose of these lateral extensions? Why would you

expect to see them at this spinal level? In slide 2, and all subsequent slides of the

spinal cord (slides 3-5), identify all of the structures you found on slide 1 .

Slide 3 (upper lumbar) appears similar to slide 2. Dentate (denticulate)

ligaments can be clearly seen in this section. What tissue layer comprises the dentate

ligaments? What are their functions?

Slide 4 (thoracic) reveals an egg shaped bulge at the medial base of the dorsal

horn. This is the dorsal nucleus of Clarke (nucleus dorsalis), an important relay

nucleus for information transmitted to the cerebellum. This slide also displays a

prominent intermediolateral gray (cell) column. What specific cell type is contained

within this column? Why is the gray matter so small in the thoracic region? Slide 5 & slide 6 reveal the transition between the cervical spinal cord and

medulla. Slide 5 is at the C-1 spinal level. Although it resembles the thoracic spinal

cord, there are some distinct differences. The intermediolateral cell column has been

replaced by the spinal accessory nucleus. How would the gray matter differ if this

were a lower cervical section? In addition, at this level the substantia gelatinosa is

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being replaced by the spinal nucleus of V (spinal trigeminal nucleus). A roughly

circular region of white matter in the lateral funiculus near the base of the dorsal horn is

separated into multiple fascicles. This is the lateral corticospinal tract, an important

descending pathway which has just decussated (crossed the midline) at more rostral

levels to assume its position within the lateral funiculus. Slide 6 is slightly more rostral

than slide 5, and represents the most caudal extent of the medulla. Find the spinal

accessory nucleus. Also note that the substantia gelatinosa has now expanded to

become the large spinal nucleus of V. The caudal extent of the decussation of the

fibers forming the lateral corticospinal tract can also be seen.

Compare the relative appearances of the spinal cord in slides 1 (sacral), 2

(lower lumbar), 3 (upper lumbar), 4 (thoracic), 5 (cervical) and be able to recognize

and identify each level by listing their major differences.

Medulla (slides 7,12)

Slide 7 is a representative section of the caudal medulla. This level is

occasionally referred to as the "closed" portion of the medulla, since it is caudal to the

fourth ventricle and thus reveals a "closed" central canal surrounded by nuclei and

fiber tracts. The prominent spinal nucleus of V can be seen. The dorsal column

region now displays a nucleus (nucleus gracilis) on either side of the midline. What

external feature reveals the location of these nuclei? The thick, black "X" at the midline

ventrally is the decussation of the pyramids, a crossing of descending nerve fibers

that will form the previously mentioned lateral corticospinal tracts seen in slide 5 & slide

6.

Slide 12 is a typical representation of the rostral medulla. This level is also

called the "open" medulla because the central canal has "opened" to form the floor of

the fourth ventricle. This level is immediately recognizable by the pyramids ventrally,

the coiled appearance of the inferior olivary nuclei, the well-defined inferior

cerebellar peduncles, fourth ventricle and overlying cerebellum. The medial

lemniscus, an important ascending sensory pathway, can be seen in the midlinesandwiched between the left and right inferior olivary nuclei. Also note the choroid

plexus within the fourth ventricle and its extension through the foramina of Luschka

to lie externally within the cerebellopontine angle. The inferior olivary nuclei cause an

external bulge, the inferior olive. Immediately ventral and dorsal to the inferior olive

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are the pre- and post-olivary sulci, respectively. What cranial nerves emerge from

each of these sulci?

Pons (slides 16,17,19)

Slide 17 is a cross section of the caudal 1/3 of the pons. The characteristic

ventral convexity of the ventral pons can be clearly seen. Imbedded within this region

are the pyramidal tracts, which are surrounded by the pontine nuclei. Dorsal to the

pyramidal tracts is the medial lemniscus. At this level, it is shaped like a handlebar

mustache and forms the dorsal border of the ventral pons. It is located in a region of

the pons called the pontine tegmentum, which extends dorsally to form the floor of the

fourth ventricle. The gently rounded floor of the fourth ventricle on either side of the

midline is called the facial colliculus. The large black areas forming the lateralboundaries of the pons at this level are the middle cerebellar peduncles (brachium

pontis). In the pontine tegmentum just medial to the middle cerebellar peduncles, the

fascicles of the facial nerve (CN VII) can be seen as they traverse the pons to emerge

caudally at the cerebellopontine angle. Identify the above pontine structures on slide

16, where the superior, inferior and middle cerebellar peduncles can be seen

simultaneously. Can you find the emerging fibers of the abducens nerve (CN VI) in

this section? Compare these sections with slide 19 (rostral pons) where you should be

able to identify the superior cerebellar peduncles, superior medullary velum, fourth

ventricle, ventral pons, pyramidal tracts, pontine tegmentum and medial

lemniscus.

Midbrain (slides 21-23)

All levels of the midbrain are characterized by the cerebral peduncles (crus

cerebri) and interpeduncular fossa ventrally, the substantia nigra (the clear region

immediately dorsal to the crus cerebri), and the medial lemniscus (dorsomedial to the

substantia nigra).The level of the inferior colliculus (slide 21) has unique characteristics, which

include the decussation of the superior cerebellar peduncles, the nucleus of CN IV

and the distinct nuclei of the inferior colliculi.

The level of the superior colliculus (slide 23) is characterized by the paired red

nuclei, nuclear complex of the oculomotor nerve (CN III) and the emerging rootlets

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of CN III as they pass through the red nuclei to emerge from the midbrain along the

walls of the interpeduncular fossa.

Slide 22 is a slightly more caudal cut through the superior collicular level. In this

slide, the red nucleus is obliterated by the crossed fibers of the superior cerebellar

peduncles as they ascend to the thalamus, and the emerging fibers of CN III. The

nuclear complex of CN III is also present.

Diencephalon (slides 23,29)

In addition to midbrain, slide 23 also contains some of the caudal structures of

the thalamus, a major subdivision of the diencephalon. These structures of the

thalamus are the pulvinar and the medial and lateral geniculate bodies. Slide 29

reveals more of the nuclei of the thalamus, including two important sensory relay nuclei,the ventral posteromedial (VPM) and ventral posterolateral (VPL) nuclei, as well as

the pulvinar. The centromedian nuclei of the thalamus, the habenular nuclei and

the mammillary bodies are also clearly seen. Midbrain structures such as cerebral

peduncles, substantia nigra and red nuclei are also present. Notice how the

cerebral peduncles merge with the posterior limb of the internal capsule. Using your

half brains, figure out the plane of section of slide 29.

NEURORADIOLOGY

Slide 52 is a midsaggital MRI through the cervical region. Identify the spinal

cord, vertebral bodies and intervertebral disks. Can you find anything abnormal or

pathological on this slide?

Slide 53 is a midsaggital MRI through the lumbar and upper sacral region. Find

the subarachnoid space, intervertebral disks and termination of the spinal cord.

Is this a T1 or T2 weighted image? Using your anatomical knowledge from Gross

Anatomy, can you identify, by number, the location of the bodies of the lumbar

vertebrae? Slides 58-65 are axial (cross section) MRI’s of the cervical spinal cord (slide 58)

through the rostral midbrain (slide 65). All of these sections are T2 weighted. Make

note that the orientation of the neuraxis on these slides is opposite to what you saw on

the stained sections (i.e., the dorsal aspect of each scan is toward the bottom of the

slide). On slide 58, note the characteristic dorsoventral flattening of the cervical spinal

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29

cord and the vertebral arteries located in the foramina transversaria. On slide 59

(caudal medulla), note the vertebral arteries, pyramids and central canal. Slide 60

(rostral medulla) clearly shows the inferior cerebellar peduncles, inferior olive and

pyramids as well as the joining of the two vertebral arteries to form the basilar artery.

At this level, the central canal has opened up into the 4th ventricle. Slide 61 (transition

from rostral medulla to caudal pons) shows the 4th ventricle, cerebellar peduncles,

CN’s VII & VIII and the basilar artery. Slide 62 (midpons) shows the middle

cerebellar peduncle, CN V as it emerges from the middle cerebellar peduncle to enter

Meckel’s cave, 4th ventricle and the basilar artery. Slide 63 (rostral pons) shows the

characteristic shape of the ventral pons, as well as the rostral extent of the 4th

ventricle, both middle and superior cerebellar peduncles and the basilar artery.

Slide 64 (caudal midbrain) shows the characteristic outline of the midbrain at this level,

including the cerebral peduncles, interpeduncular fossa and inferior colliculus. Atthis level, the superior cerebellar arteries can be seen arising from the basilar artery

to embrace the midbrain. The internal carotid arteries, uncus and temporal horn of

the lateral ventricles can also be seen in this slide. Slide 65 (rostral midbrain) shows

a number of structures including cerebral peduncles, interpeduncular fossa,

superior colliculi, red nuclei, mammillary bodies, hypothalamus, uncus and third

ventricle. In addition, the posterior cerebral, middle cerebral, anterior cerebral and

internal carotid arteries can be seen as well as the superior cerebellar cistern. To

verify what you are seeing on slide 65, compare it to a similar horizontal wet brain

section.

NOTES

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30

ASCENDING SENSORY PATHWAYS

Objectives: 1. Know the location and function of each of the described pathways at all

levels of the neuraxis, from their origin to their termination in the

cerebral cortex.

2. Be able to determine the clinical signs and symptoms resulting from

lesions of these pathways at any level of the neuraxis.

There are a number of ascending pathways in the neuraxis that carry a variety of

different types (modalities) of sensory information from the body, extremities and head

to the cerebral cortex. Those dealing with the body, extremities and posterior 1/3 of the

head receive their input from the dorsal roots of spinal nerves. Those pathways

transmitting sensory information to the cortex from the anterior 2/3 of the head (i.e. face,nasal cavities, oral cavity, pharynx, larynx, etc.) receive their input from the cranial

nerves. We will concentrate our efforts on those pathways that are clinically relevant

and produce consistent, repeatable sensory deficits when lesioned (injured).

In studying these pathways, it is best to follow each one from its origins in the

spinal cord to its thalamic terminations using the slide set. The final portions of these

pathways from thalamus to cerebral cortex can be seen on demonstration and on your

wet brain specimens.

Ascending sensory pathways from the body and posterior 1/3 of the head -- The

first order (1o) neurons (the first neuron in the pathway) for all sensory pathways from

the body and posterior 1/3 of the head reside in the dorsal root ganglia of the spinal

nerves. The central processes of these cells enter the spinal cord via the dorsal roots to

either synapse in the spinal cord and/or ascend to brainstem levels. The nerve fibers in

these sensory pathways are typically arranged in a somatotopic fashion throughout their

ascent through the spinal cord, brainstem and telencephalon.



31

1. Anterolateral System (Spinal Lemniscus)

a. Lateral spinothalamic tract [Modalities: pain and temperature]

b. Anterior (ventral) spinothalamic tract [Modalities: crude (light) touch]

c. Spinotectal tract [Modality: pain]. This pathway is the afferent limb of

a “reflex pathway that results in reflexive turning of the head and eyes

in response to a painful (nociceptive) stimulus.

These pathways will be studied together since they occupy similar positions

within the neuraxis. They are listed above in descending order of their relative clinical

importance. The lateral spinothalamic tract is, by far, the most important pathway.

First order neurons for these pathways lie in the dorsal root ganglia in all spinal nerves

(except C-1). The central processes of these cells terminate in the dorsal horn ineither the substantia gelatinosa or the nucleus proprius. Second order (2o) neurons

in these nuclei give rise to axons that cross the midline in the anterior white

commissure to assume a peripheral position in the ventral aspect of the contralateral

lateral funiculus as the lateral spinothalamic tract (and spinotectal tract), or a slightly

more ventral position (anterior spinothalamic tract) (slide 1, slide 2, slide 3, slide 4,

and slide 5). As these fibers cross the midline, they ascend 1-3 spinal segments before

they join their respective contralateral fiber tracts. How would this bit of knowledge

affect the level of sensory deficits if a lesion of the lateral spinothalamic tract occurred at

the T-10 spinal level?

These three pathways ascend together throughout the spinal cord and

brainstem, and are often referred to collectively as the spinal lemniscus or

anterolateral system. When they enter the medulla, they can be found in the lateral

aspect just dorsal to the inferior olivary nucleus (slide 9, slide 10, slide 12, slide 13,

slide 14 and slide 15). In the pons and midbrain (slide 16, slide 17, slide 18, slide 19,

slide 20, slide 21, slide 22, slide 23 and slide 24) the spinal lemniscus can be found

lateral to the medial lemniscus. At the level of the superior colliculus, the fibers of the

spinotectal tract peel off to terminate in the superior colliculus. The remaining lateraland anterior spinothalamic tracts continue rostrally to terminate in the ipsilateral ventral

posterolateral (VPL) nucleus of the thalamus, where third order (3o) neurons in the

VPL then project their axons to the postcentral gyrus via the posterior limb of the

internal capsule (slide 28, slide 29, slide 30 and slide 31) and corona radiata (see

demonstration). NOTE: As the spinal lemniscus proceeds rostrally through the



















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brainstem, the lateral and anterior spinothalamic tracts give off extensive collateral

axons to the reticular formation (RF) at all brainstem levels. You will learn about the RF

later in the course.

2. The Dorsal Column / Medial Lemniscus Pathway [Modalities: fine tactile

(touch & pressure), vibration, proprioception/kinesthesia (position/movement

sense)]

This ascending pathway is anatomically and functionally separated into two distinct

pathways within the dorsal columns of the spinal cord. Central processes from dorsal

root ganglia (1o neurons) gain access to the spinal cord and ascend in the ipsilateral

dorsal column without synapsing in the spinal cord. Information coming into the spinal

cord from the lower extremities up to approximately the T-7 spinal level, form a singleipsilateral pathway in the dorsal columns called the fasciculus gracilis (slide 1, slide

2, slide 3 and slide 4). The central processes for dorsal root ganglion cells from T-6 up

through C-2 (C-1 spinal nerves have no dorsal root ganglia) ascends in the dorsal

columns lateral to the fasciculus gracilis as the fasciculus cuneatus (slide 5 and slide

6). As these pathways ascend into the medulla, they remain in their same relative

positions (slide 6). The fasciculus gracilis terminates in the nucleus gracilis, which

appears at more caudal levels, while the fasciculus cuneatus continues to ascend to

more rostral levels of the medulla to terminate in the nucleus cuneatus (slide 7 and

slide 8). What external features signal the underlying presence of the nucleus gracilis

and nucleus cuneatus? Second order (2o) neurons in the nucleus gracilis and nucleus

cuneatus give rise to axons that sweep ventrally as the internal arcuate fibers to cross

the midline (sensory decussation/decussation of the medial lemniscus) and form

the contralateral ascending fiber bundle called the medial lemniscus (slide 8). These

axons then ascend somatotopically within the medial lemniscus through the medulla

(slide 9, slide 10, slide 12, slide 13 and slide 14), pons (slide 16, slide 17, slide 18,

slide 19 and slide 20) and midbrain (slide 21, slide 22, slide 23, slide 24 and slide

26) to terminate on third order (3o) neurons located in the ipsilateral ventral

posterolateral (VPL) nucleus of the thalamus (slide 28, slide 29 and slide 30).

Third order (3o) neurons in the VPL give rise to axons that gain access to the posterior

limb of the internal capsule (slide 28, slide 29, slide 30 and slide 31). These axons

then fan out in the corona radiata (see demonstration) to terminate primarily in the

postcentral gyrus (Brodmann's areas 3,1,2).



























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33

DEMONSTRATIONS

Posterior Limb of the Internal Capsule.

Corona Radiata.

Postcentral Gyrus (Brodmann’s areas 3,1,2).

NOTES



34

SENSORY PATHWAYS FOR THE ANTERIOR 2/3 OF THE HEAD

Objectives: 1. Know the location and function of each of the described pathways from

their origin to their termination in the cerebral cortex.


lesions of these pathways at any point in their travels.

The vast majority of sensation from the external surface of the anterior 2/3 of the

head is provided by the trigeminal nerve (CN V) by way of its three divisions

(ophthalmic, maxillary and mandibular) with the remainder being supplied by CN VII, IX

and X. With the exception of proprioception and possibly pressure, the 1o neurons in

each of the following pathways are located in the sensory ganglia associated with each

of the above nerves. For the modalities of pain and temperature, the central processesfrom each of these sensory ganglia have the same central pathways.

1. Pain and Temperature -- On your whole brain specimens, find CN V, VII, IX and X

and make careful note of where they emerge from the brainstem. Now observe slide

16 and slide 17. These are cross sections through the caudal pons. On both slides,

note the facial colliculus forming the floor of the fourth ventricle, and the fascicles of

CN VII as they arch through the pontine tegmentum to exit the brainstem ventrally.

Just lateral to the axons of CN VII in the pontine tegmentum is a relatively clear, oval

area, the spinal nucleus of V. Surrounding the spinal nucleus of V on the lateral side

is a kidney-shaped area of nerve fibers, the descending (spinal) tract of V. Note the

close proximity of the spinal tract of V to the emerging fibers of CN VII. The descending

tract of V contains descending fibers of the central processes of the ipsilateral trigeminal

ganglion. As this tract descends, it picks up descending nerve fibers from the sensory

ganglia of CN VII, IX and X. These nerve fibers terminate in the spinal nucleus of V.

Both the spinal tract and nucleus of V are present from this point (i.e., caudal pons)

caudally to the level of the upper cervical spinal cord, where they are replaced by

Lissaur's tract and the substantia gelatinosa, respectively. Verify this by followingthe spinal tract and nucleus of V caudally (slide 17, slide 16, slide 15, slide 14, slide

13, slide 12, slide 10, slide 9, slide 8, slide 7, slide 6 and slide 5). As you do this,

note the close proximity of the spinal tract of V to the emerging fibers of CN VII (slide

17 and slide 16), CN IX (slide 14) and CN X (slide 12). 2o neurons in the spinal

nucleus of V give rise to axons that cross the midline obliquely and ascend as the














































































35

ventral trigeminothalamic tract (trigeminal lemniscus). (NOTE: There is still some

uncertainty as to the exact location of this tract in humans. The brain atlases show this

tract scattered dorsolateral to the medial lemniscus in the medulla. For the sake of your

collective sanity, we will not require you to know the location of the trigeminal lemniscus

in the medulla). As the medial lemniscus flattens dorsoventrally in the pons (slide 16,

slide 17, slide 18, slide 19 and slide 20), the trigeminal lemniscus remains on its

dorsal aspect, sandwiched between the medial lemniscus and the overlying central

tegmental tract.

In the midbrain, the trigeminal lemniscus assumes a position along the medial

concave surface of the medial lemniscus as the latter fans out laterally and dorsally

(slide 21, slide 22, slide 23 and slide 24) to assume a more vertical orientation. The

ascending 2o axons in the trigeminal lemniscus terminate in the ventral posteromedial

nucleus (VPM) of the thalamus (slide 29 and slide 30). 3o

neurons in the VPM giverise to axons that travel through the posterior limb of the internal capsule (slide 28,

slide 29, slide 30 and slide 31) and through the corona radiata (see demonstration) to

terminate in the postcentral gyrus near the Sylvian fissure.

2. Fine Touch, Vibration and Pressure -- The central processes of the trigeminal

ganglion cells course into the mid pons via CN V and terminate ipsilaterally on the

enlarged rostral extension of the spinal nucleus of V, called the chief (principal)

sensory nucleus of V. This nucleus lies in the lateralmost aspect of the pontine

tegmentum just medial to the middle cerebellar peduncle (slide 18). The 2o neurons

in this nucleus give rise to axons that cross the midline obliquely and ascend to join the

trigeminal lemniscus at midbrain levels (slide 21, slide 22, slide 23 and slide 24).

These nerve fibers then follow the exact synaptic pathway to the cortex as described

above for pain and temperature fibers for the anterior 2/3rds of the head. How would

the symptoms differ in a lesion of the trigeminal lemniscus in the caudal pons, as

opposed to a lesion of this structure at the superior collicular level?

3. Proprioception [and pressure (?)] -- In the case of proprioception, and possiblypressure, the 1o neurons in this pathway do not lie in the trigeminal ganglia, but instead

lie within the mesencephalic nucleus of V, which resides in the brainstem from the

mid pons to the superior collicular level of the midbrain. In the mid pons, this nucleus

lies dorsomedial to the chief sensory nucleus of V (slide 18). The peripheral processes

of these cells join CN V to be distributed with the three divisions of this nerve. They

















































































36

accomplish this by forming a small, sickle shaped fascicle of nerve fibers immediately

ventrolateral to the mesencephalic nucleus of V. These fibers are called the

mesencephalic root (tract) of V (slide 18). In the midbrain (slide 21 and slide 22),

the mesencephalic nucleus of V can be seen as a lateral outpocketing of the

periaqueductal gray at the approximate level of the floor of the cerebral aqueduct.

The mesencephalic root of V can be seen as a thin rim of fibers surrounding the

lateral aspect of the nucleus. The central processes of the mesencephalic nucleus of V

establish multiple contacts with the reticular formation (RF) of the pons and midbrain. It

is thought that the RF, through multiple, diffuse, bilateral (and unknown) synaptic

pathways, eventually transmits proprioceptive information to the cerebral cortex, either

directly or through the thalamus.

DEMONSTRATIONS

Internal Capsule.

Corona Radiata.

Postcentral Gyrus (Broadmann’s areas 3,1,2).

NOTES














37

THE PYRAMIDAL SYSTEM

Objectives: 1. Know the location and function of each of the described pathways at all

levels of the neuraxis from their origin in the cerebral cortex to their

termination in the brainstem and/or spinal cord.


lesions of these pathways at any level of the neuraxis in which they are

located.

The term "pyramidal system" refers to the direct (through internuncial cells),

volitional (voluntary) motor pathways from the cerebral cortex to the motor nuclei that

control the voluntary muscles of the body, extremities and head. Conversely, the term

"extrapyramidal system" (to be studied later) refers to motor pathways from the cerebralcortex that form loops with the basal ganglia and thalamus, and function in more

stereotypic movements and maintenance of posture.

Although the terms "pyramidal system" and "extrapyramidal system" are old

terms that have come into disrepute in recent years as our knowledge of the functioning

of the nervous system grows, they still cling to life among both basic scientists and

clinicians. Classically, the pyramidal system is subdivided into two parts: 1) the

corticobulbar tract, which terminates on cranial nerve motor nuclei within the

brainstem and thus controls the voluntary muscles of the head (and some in the neck),

and 2) the corticospinal (pyramidal) tract, which provides descending nerve fibers

from the cortex to the motor cell columns in the spinal cord for voluntary movement of

the body and extremities. Since these two pathways have identical functions in their

respective areas of innervation, and follow similar paths through brainstem levels, they

will be studied together.

Whole and Half Brains; Horizontal and Coronal Sections

Although there are significant contributions from other areas of the cerebralcortex (Brodmann's areas 6,8,3,1,2,5), both the corticobulbar and corticospinal tracts

begin primarily in the precentral gyrus (Brodmann's area 4). Find these regions on

your whole and/or half brains. The cortical neurons that reside in the above regions are

called upper motor neurons. These upper motor neurons are located somatotopically

within the precentral gyrus. The neurons for the corticobulbar tract are located near the



38

Sylvian fissure, whereas the neurons for the corticospinal tract reside somatotopically

in the remainder of the precentral gyrus as it arches dorsally and medially. Study

the motor homunculus on your lecture handout and make sure you understand this

concept. Axons arising from these upper motor neurons descend through the corona

radiata, which converges into the relatively compact internal capsule (observe these

structures on both your horizontal and coronal sections). The corticobulbar fibers

assume a compact position within the genu of the internal capsule, which resides at

the rostral pole of the thalamus. The corticospinal axons reside in a compact,

somatotopic fashion toward the caudal extent of the posterior limb of the internal

capsule. Can you think of a possible negative consequence related to the compact

nature of the corticobulbar and corticospinal fibers as they descend through the internal

capsule? As we descend from diencephalic to midbrain levels, each internal capsule is

continuous inferiorly with the ipsilateral cerebral peduncle. Compare and contrast theappearance and relationship of the internal capsule and cerebral peduncles on the

horizontal and coronal slices. This relationship can often be seen particularly well on

your coronal slices where the posterior limb of the internal capsule blends inferiorly

with the cerebral peduncles. Observing both coronal and horizontal slices, what

structure always resides immediately medial to the posterior limb of the internal

capsule?

As the corticobulbar and corticospinal axons descend into the midbrain, they are

classically described as residing in the middle 3/5 of the cerebral peduncles, with the

corticobulbar fibers occupying the medial portion and the corticospinal fibers arranged

somatotopically with lower extremity fibers most lateral. The cerebral peduncles can

usually be seen cut in cross section on the most inferior horizontal brain slice.

Now look on the ventral surface of your whole brain and note that the cerebral

peduncles terminate by disappearing caudally into the convexity of the ventral pons.

The pyramidal (corticospinal) tract emerges caudally in the medulla as the pyramids.

"What happened to the corticobulbar tract?", you may ask. Good question! (Try to

figure this out before you read on). The following is a good answer. As the

corticobulbar tract descends through the midbrain and pons, nerve fibers from this tractare peeling off to synapse on the motor nuclei of CN III, IV, V, VI and VII. The

remaining fibers for the medullary motor nuclei [nucleus ambiguus (motor nucleus for

CN IX, X and XI) and the hypoglossal nucleus] have also begun to separate from the

corticospinal fibers in the caudal pons to arch dorsally to synapse on these nuclei.

Consequently, the vast majority of the nerve fibers in the pyramids are those of the



39

pyramidal (corticospinal) tract. Find the longitudinal median fissure between the

pyramids in the rostral medulla. As you follow this distinct fissure caudally, it will blur, or

fill in, at the level of the caudal medulla. This is caused by the pyramidal decussation,

the crossing of the pyramidal tract to form the lateral corticospinal tract within the

spinal cord. Although a small percentage of fibers do not decussate, they are typically

not clinically relevant.

Slide Set (Don't put your brains away yet!)

Now, using your slide set and your atlas, follow the respective pathways of the

corticospinal and corticobulbar tracts. Begin with slide 35, which is a horizontal section

through the diencephalon at the level of the interventricular foramina of Monro. The

rostral direction is toward the top of the slide. Identify the anterior limb, genu and posterior limb of the internal capsule. Also note the columns of the fornix, third

ventricle and thalamus. Now, find a slice from your horizontally sectioned wet brain

specimen that compares to slide 35 and find the same structures as discussed above.

Note, on both the slide and the brain slice, the anatomical relationship between the

posterior limb of the internal capsule and the thalamus. It is strongly suggested that you

remember this relationship, since it is a consistent one that serves to identify these

structures in a variety of planes.

Now view slide 32. This is roughly a coronal section through the mid thalamus.

Find the thalamus, posterior limb of the internal capsule, third ventricle and

massa intermedia. What is the space immediately dorsal to the massa intermedia?

As you did previously, find a comparable coronal slice from your wet brain specimens

and compare it to this slide while you identify the above structures.

Slide 31, slide 30 and slide 29 show the transition between the posterior limb

of the internal capsule and the cerebral peduncles. Identify these structures, as well

as the thalamus and third ventricle. Slide 28 is particularly interesting, since it

provides a roughly coronal view of the diencephalon and oblique views of both midbrain

and pons. Using your half brain or one of your coronal sections for comparison, figureout the plane of section of this slide.

Using slide 24, slide 23, slide 22 and slide 21, follow and identify the

corticospinal and corticobulbar tracts caudally through the midbrain, noting the general

location and somatotopic arrangement of these tracts in the cerebral peduncles. On

slide 20, slide 19, slide 18, slide 17 and slide 16, notice how these tracts are

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separated into loosely arranged fascicles in the ventral pons. The fascicles of the

corticobulbar tract are represented in the dorsomedial region of these fascicles. Slide

15 illustrates the medullary-pontine junction. The caudal remnants of the ventral

pons can be seen at the bottom of the slide. The pyramidal tracts have coalesced to

form two distinct fiber bundles, the pyramids, ventral to the inferior olivary nuclei. At

this level, only a few fascicles of the corticobulbar tracts remain.

Slide 14, slide 13, slide 12, slide 10 and slide 9 show the typical, consistent

appearance and location of the pyramids from rostral to caudal medulla. Slide 8

illustrates the beginning of the pyramidal (motor) decussation. The median fissure

between the pyramids is displaced to the right at its apex and the dorsomedial region of

the right pyramid is beginning to move dorsally. The remaining rostrocaudal extent of

the pyramidal decussation is illustrated in slide 7 and slide 6, which demonstrate the

fibers of the pyramidal tract crossing the midline to assume a more dorsolateral location.Once these fibers attain their new position contralaterally, they are called the lateral

corticospinal tract. Slide 5 (spinal cord level C-1) shows the location of the lateral

corticospinal tracts as loose fascicles of nerve fibers tucked into the concavity along

the lateral surface of the dorsal and ventral horns. The lateral corticospinal tract

maintains this position throughout the spinal cord (slide 4, slide 3, slide 2 and slide 1).

Would the symptoms be the same in an individual with a lesion of the right pyramid and

another individual with a lesion of the right lateral corticospinal tract? Can you explain

and coherently defend your answer?

DEMONSTRATIONS

Corona Radiata, Internal Capsule, Cerebral Peduncles.

Pyramidal Decussation.

NOTES





















































41

CRANIAL NERVES

Objectives: 1. Be able to locate and identify the cranial nerves on the wet brains, and

understand the various functions of each.

2. Demonstrate a general understanding of “functional components” as

described in this section.


lesions involving all components of CN’s I, III, IV, V, VI, VII, IX, X, XI,

XII.

There are twelve pairs of cranial nerves. A lesion to any one of these nerves

results in clinically demonstrable deficits. As such, any general neurological exam

should include an assessment of cranial nerve function. The purpose of this laboratorysession is twofold: 1) to (re)acquaint you with the gross anatomy of the cranial nerves,

and 2) to study the internal macroscopic anatomy of selected cranial nerves (CN I, III,

IV, V, VI, VII, IX, X, XI and XII). The remaining cranial nerves (CN II and VIII) will be

studied, in detail, in subsequent laboratory sessions.

In the classic description of cranial nerves (and spinal nerves), each type of

nerve fiber contained within a given nerve (i.e. sensory, motor, autonomic, etc.) is

assigned a unique descriptive nomenclature to describe their general function. Each of

these descriptive terms is called a functional component. Although the importance of

the concept of functional components is dwindling, they provide an organized way to

categorize nerve fiber function. The following is a list of the functional components

found in the cranial nerves:

1. General Somatic Afferent (GSA) -- sensory nerve fibers that serve the skin as well

as the oral and nasal cavities and include "general" sensations such as touch, pain,

pressure, etc.

2. General Visceral Afferent (GVA) -- sensory nerves serving visceral structures

(pharynx, larynx, esophagus, gut, blood vessels, etc.) and carrying "general"

sensations as described above.

3. Special Visceral Afferent (SVA) -- the "special visceral" senses of taste and smell.

4. Special Somatic Afferent (SSA) -- the "special" senses of hearing, balance and

vision.



42

5. General Somatic Efferent (GSE) -- motor nerve fibers that innervate voluntary

(striated) muscles other than those of branchiomeric (pharyngeal arch) origin.

6. General Visceral Efferent (GVE) -- autonomic nerve fibers (both parasympathetic

and sympathetic, pre- and postganglionic).

7. Special Visceral Efferent (SVE) -- motor nerve fibers that innervate muscles of

branchiomeric origin (muscles of mastication, facial expression, pharynx, larynx,

etc.).

Whole and Half Brains

Using your whole and half brains, turn them over to view the ventral surface and

observe the following:

CN I (olfactory nerve) -- This nerve provides us with our sense of smell (SVA). In

addition to its unique sensory function, the primary olfactory pathway is also unique

among the sensory pathways in that it does not have a relay through the thalamus to

the cerebral cortex, but instead sends projections directly to phylogenetically older

cortical areas (paleocortex). Another unique aspect of the olfactory pathway is the lack

of a decussation, i.e. the pathway is ipsilateral. The 1o cell bodies in this pathway are

located in the upper reaches of the nasal cavity. The actual filaments (axons) of CN I

extend through the cribriform plate of the ethmoid bone as the olfactory nerves, whichpenetrate the olfactory bulbs to synapse with the 2o neurons located there.

On the ventral surface of the brain, the olfactory bulbs can be seen on the

surface of the frontal lobes near the midline. The olfactory tract (stalk) extends

caudally from the olfactory bulb, carrying the axons of 2o neurons. As the olfactory tract

approaches the anterior perforated substance, it divides into medial and lateral

olfactory stria, each stria forming the sides of a triangular region called the olfactory

trigone. The medial olfactory stria crosses the midline via the anterior commissure to

supply interconnections between the left and right olfactory bulbs. Consequently, the

lateral olfactory stria is the principal central projection pathway for the olfactory system.

Follow the lateral olfactory stria as it heads toward the region of the uncus, where it

synapses in the primary olfactory cortex (periamygdaloid cortex, piriform cortex) and

the amygdala, a cluster of subcortical nuclei located deep to this paleocortex.

Secondary connections from these areas project to the rostral region of the



43

parahippocampal gyrus (entorhinal cortex), hippocampus (not seen here) and

hypothalamus. It should also be noted that the hypothalamus, thalamus,

parahippocampal gyrus and amygdala form part of the limbic system, the "emotional"

part of our brain.

CN II (optic nerve) -- This nerve is for vision (SSA). The optic nerves are seen in the

midline just caudal to the olfactory tracts. The left and right optic nerves meet at the

midline and fuse, forming the optic chiasm. Note the relationship of the infundibulum

and the optic chiasm. Two diverging nerve bundles, the optic tracts, can be seen

arching laterally and posteriorly from the optic chiasm to interconnect with the

diencephalon and midbrain.

CN III (oculomotor nerve) -- This nerve supplies motor innervation (GSE) to theextraocular muscles with the exception of the superior oblique and lateral rectus

muscles. In addition, it provides preganglionic parasympathetic fibers (GVE) to the

ciliary ganglion, which, in turn, provides postganglionic parasympathetic innervation to

the sphincter pupillae muscles and the muscles of the ciliary body that control the shape

of the lens. The oculomotor nerve can be seen emerging from the walls of the

interpeduncular fossa between the cerebral peduncles of the midbrain. As it

emerges, it passes between the posterior cerebral and superior cerebellar arteries

before eventually passing into the orbit via the superior orbital fissure.

CN IV (trochlear nerve) -- This small, threadlike nerve supplies motor innervation to the

superior oblique muscle of the orbit (GSE). If present, it can be seen along the lateral

aspect of the cerebral peduncles near their junction with the ventral pons. It is the

only cranial nerve to emerge from the dorsal aspect of the brainstem. NOTE: Do not

attempt to view this nerve on your brain specimens as it emerges from the dorsal

midbrain. This can be seen on demonstration. After emerging just caudal to the

inferior colliculi, it arches ventrally around the caudal midbrain to dive between the

layers of dura mater forming the anterolateral border of the tentorial notch. It gainsaccess to the orbit via the superior orbital fissure.

CN V (trigeminal nerve) -- This nerve supplies sensory innervation (GSA) to the

anterior 2/3 of the head, oral and nasal cavities and soft palate. In addition to supplying

motor (SVE) and proprioceptive innervation (GSA) to the muscles of mastication, it also



44

supplies motor (SVE) and proprioceptive (GSA) innervation to the myelohyoid, anterior

belly of digastric, tensor tympani and tensor veli palatini muscles. It is also thought to

supply proprioceptive fibers to the extraocular muscles. This large nerve emerges from

the rostral border of the middle cerebellar peduncle along the lateral aspect of the

pons to enter Meckel's cave, where the trigeminal (semilunar) ganglion resides. Distal

to the ganglion, CN V separates into its three divisions (ophthalmic, maxillary and

mandibular).

CN VI (abducens nerve) -- This nerve supplies motor innervation (GSE) to the lateral

rectus muscle of the orbit. It can be found near the midline, emerging from the inferior

pontine sulcus at the medullary-pontine junction. It courses anteriorly to gain access

to the orbit via the superior orbital fissure.

CN VII (facial nerve) -- This complex nerve gives motor innervation (SVE) to the

muscles of facial expression as well as the stapedius, posterior belly of the digastric and

stylohyoid muscles. In addition, preganglionic parasympathetic innervation (GVE) is

supplied (via parasympathetic ganglia containing postganglionic neurons) to the lacrimal

gland, the submandibular and sublingual salivary glands, as well as the mucous

membranes of the hard palate, soft palate and nasal cavities. It also contains sensory

nerve fibers that convey taste (SVA) from the anterior 2/3 of the tongue (and soft and

hard palates) and general sensation (GSA) from the external ear. This nerve can be

seen as it emerges at the cerebellopontine angle. What foramen does it traverse to

gain access to the facial canal?

CN VIII (vestibulocochlear nerve) -- This sensory nerve conducts auditory information

(SSA) from the cochlea and information for equilibrium from the semicircular canals. It

emerges just lateral to the facial nerve in the cerebellopontine angle and enters the

same foramen as the facial nerve.

CN IX (glossopharyngeal nerve) -- This nerve provides motor innervation (SVE) to thestylopharyngeus muscle. It also contains preganglionic parasympathetic nerve fibers

(GVE) destined for the otic ganglion. Postganglionic fibers from this ganglion are

secretomotor to the parotid gland. The sensory nerve fibers in this nerve provide taste

(SVA) and general sensation (GVA) from the posterior 1/3 of the tongue. It also

provides general sensation from the palatine tonsils (GVA), middle ear (GVA) and



45

external ear (GSA), and information from the carotid body and sinus (GVA). This nerve

emerges from the postolivary sulcus immediately caudal to CN VIII to pass into the

jugular foramen.

CN X (vagus nerve) -- This nerve provides motor innervation (SVE) to the muscles of

the pharynx (except stylopharyngeus), larynx and soft palate (except tensor veli

palatini). In addition, it provides preganglionic parasympathetic fibers (GVE) to

parasympathetic ganglia that innervate smooth muscles and glands in the larynx,

pharynx and all thoracic and abdominal viscera down to the left colic flexure. It also

provides sensory innervation to these same structures (GVA) as well as taste (SVA) to

the epiglottis and sensory innervation to the external ear (GSA). This nerve emerges

from the postolivary sulcus immediately caudal to CN IX as several compact rootlets

arranged in a rostrocaudal fashion and exits the skull via the jugular foramen.

CN XI (spinal accessory nerve) -- This nerve provides motor innervation (GSE) to the

trapezius and sternocleidomastoid muscles. It will not be present on your specimens,

since it arises from the lateral aspect of the upper cervical spinal cord to ascend through

the foramen magnum and assume a position along the lateral aspect of the medulla

before it exits the skull through the jugular foramen.

CN XII (hypoglossal nerve) -- This nerve provides motor innervation (GSE) to the

intrinsic and extrinsic muscles of the tongue. It exits the brainstem as a series of

loosely arranged rostrocaudal rootlets arising from the preolivary sulcus. These

rootlets converge to exit the skull via the hypoglossal canal.

Slide Set

CN III (slides 24-22) -- Begin with slide 24. This is a section through the rostral

midbrain. The gray matter that lies dorsomedial to the red nuclei contains the

oculomotor nuclear complex. Within this region are separate nuclei that control eachof the extraocular muscles innervated by CN III (Don't panic! You will not be asked to

identify each of these individual nuclei). In addition, this nuclear complex contains two

small, almond shaped nuclei that lie on its dorsal aspect. These are the Edinger-

Westphal nuclei. What specific cell type is contained in the Edinger-Westphal nuclei?

Although close to the midline, each of the nuclei within the oculomotor nuclear complex






46

gives rise to axons that remain ipsilateral to form CN III on their respective sides. The

boomerang shaped white matter immediately lateral to the oculomotor nuclei is the

medial longitudinal fasciculus (MLF). This important fiber tract contains axons that

interconnect the motor nuclei of CN III, IV and VI. Can you speculate why these nuclei

should be interconnected?

On slide 23, find the above structures, including the emerging fibers of CN III

along the lateral walls of the interpeduncular fossa. As these fibers emerge from the

oculomotor nuclear complex, they fan out laterally and ventrally to penetrate the red

nucleus before they swerve medially to exit the midbrain ventrally. This phenomenon

can be seen clearly on slide 22.

CN IV (slides 21,20) -- On slide 21, the trochlear nucleus replaces the Edinger-

Westphal nucleus just ventral to the periaqueductal gray. The small fascicle of axonsarising laterally from each nucleus is CN IV as it begins its journey to the dorsal aspect

of the pons by arching laterally and dorsally. The medial longitudinal fasciculus can

be seen just ventral to the trochlear nuclei and as a thin horizontal strip across the

midline. What specific level of the midbrain is represented in this slide?

Slide 20 (rostral pons) is caudal to the trochlear nucleus, a structure of the

midbrain. However, it shows the fibers of CN IV in two perspectives: 1) as the axons

of CN IV arise from the trochlear nucleus, they turn caudally to form a tight fascicle of

fibers in the lateral reaches of the periaqueductal gray, and 2) upon reaching the

rostral pons, the fibers of CN IV cross the midline within the superior medullary velum

as the decussation of CN IV to emerge from the dorsum of the brainstem as the

contralateral CN IV. With this in mind, what clinical symptom(s) would you expect to

see following a lesion of the right trochlear nucleus? Also note the medial longitudinal

fasciculus along the floor of the periaqueductal gray.

CN V (slides 23-20,18-12,10-6) -- Many of the major central components of this nerve

have been covered previously under the section entitled "Sensory Pathways for the

Anterior 2/3 of the Head" (pp. 34-36). Go back and review that section now, then comeback to this section for additional information.

Slide 18 (middle 1/3 of pons) shows all the central sensory and motor structures

of V with the exception of the spinal nucleus and tract of V, which reside at more caudal

levels. Reacquaint yourselves with the middle cerebellar peduncle, chief sensory

nucleus of V, and the mesencephalic tract and nucleus of V. Just medial to the



















47

chief sensory nucleus of V is a small fascicle of nerve fibers, the motor root of V.

These fibers originated from the clear, egg shaped area, the motor nucleus of V,

located just medial to the motor root of V. This motor nucleus supplies the muscles

innervated by CN V. Do you remember what they are? Find the MLF on this slide.

CN VI and CN VII (slides 17-15) -- These three slides show the caudal 1/3 of the pons.

Slide 17 and slide 16 are essentially at the same level and show many of the same

structures. On each of these slides, find the following: fourth ventricle, middle

cerebellar peduncles, medial lemniscus and pyramidal tracts. The floor of the

fourth ventricle shows a groove at the midline, flanked by gently sloping mounds called

the facial colliculi. The clear oval areas immediately subjacent to the facial colliculi are

the left and right nuclei of CN VI. Is this a motor or sensory nucleus? Arising from the

medial surface of the nucleus of CN VI, and coursing ventrally through the mediallemniscus, are the small fascicles of axons forming CN VI. Just medial to the nucleus of

CN VI lie two fasciculi, the more dorsal one is the (internal) genu of CN VII. The other

is the MLF. Note the close proximity of the MLF and the nucleus of CN VI. The fascicle

of axons arching ventrolaterally from the lateral aspect of the floor of the fourth ventricle

is CN VII. Just medial to CN VII in the ventrolateral reaches of the pontine tegmentum

is an oval area, the motor nucleus of CN VII. What nucleus and its associated

pathway lie just lateral to CN VII in the pontine tegmentum? CN VII can also be seen

externally as it emerges just lateral to the ventral pons (slide 16 also shows CN VIII).

At this point, it is critical to understand the internal path of axons arising from the

motor nucleus of CN VII. After arising from the nucleus, these axons travel

dorsomedially (cannot be seen here) to pass just caudal to the nucleus of CN VI and lie

at the floor of the fourth ventricle near the midline. At this point, they bend rostrally

(internal genu of CN VII) to ascend to the rostral pole of the nucleus of CN VI. They

then arch over the nucleus of CN VI and proceed ventrally and caudally to exit the

brainstem. How does this compare to the internal path of CN IV?

It should also be noted (but not seen) that the superior salivatory nucleus lies

on the dorsomedial aspect of each facial nucleus. This important autonomic nucleussupplies preganglionic parasympathetic nerve fibers (GVE) via CN VII that are

secretomotor to the lacrimal gland (via the pterygopalatine ganglion), and to the

submandibular and sublingual salivary glands (via the submandibular ganglion).

Externally, just medial to CN VIII, some fascicles of CN VII can be seen.













48

Slide 15 shows the medullary-pontine junction. The spinal nucleus of V can

be seen just medial to the inferior cerebellar peduncle. On the right side, the small

nuclear area immediately dorsomedial to the spinal nucleus of V, and just medial to the

speckled region, is the rostral extent of the nucleus solitarius. The thin rim of white

matter immediately lateral to this nucleus is the fasciculus (tractus) solitarius. This

nucleus and its related tract conduct primarily taste information from CN VII, IX and X

(taste pathway will be discussed shortly). The small oval nuclear region just medial to

the nucleus solitarius contains the rostral extent of the inferior salivatory nucleus

(GVE). This nucleus is associated with CN IX. Externally, CN VII can be seen just

lateral to the postolivary sulcus on the left side. A lesion of this nerve would cause what

clinical symptom(s)?

CN IX (slides 29,19-12,10,9) -- Begin with slide 14 (rostral medulla). On the right side,CN IX can be clearly seen emerging from the postolivary sulcus. The pale area

immediately dorsomedial to the concavity of the postolivary sulcus contains the nucleus

ambiguus. This diffuse motor nucleus (SVE) resides in the rostral medulla and

contributes axons to both CN IX and X. It supplies innervation to the muscles of

branchiomeric origin supplied by these two cranial nerves. If you are having difficulty

finding this nucleus, do not despair. It lives up to its name in that it is difficult, at best, to

pinpoint in any given section. You will have your best luck finding it in slide 12 and

slide 15 (right side).

In addition to SVE innervation, CN IX also supplies GVE fibers in the form of

preganglionic parasympathetic axons to the otic ganglion for salivary secretions from

the parotid gland. These fibers are contributed by the inferior salivatory nucleus. This

small nucleus lies just medial to the nucleus solitarius (don’t worry about trying to find

it, just know that it resides in this area).

Slide 13, slide 12, slide 10 and slide 9 illustrate the location of the nucleus and

tractus solitarius. These bilateral structures gradually approach each other to fuse at

the midline caudal to the obex. What is the obex and at what level of the neuraxis is it

located? Although these structures extend into the caudal medulla, it should be notedthat 2o taste (gustatory) efferents from this nucleus arise from the rostral-most portion of

the nucleus.

Most of the efferent nerve fibers from the nucleus solitarius form the primary

ascending taste pathway, which is located primarily in the ipsilateral central tegmental

tract. In the rostral medulla, the central tegmental tract is located immediately dorsal to































49

the inferior olivary nuclei (slide 9, slide 12 and slide 13). In the caudal half of the pons,

it is located just dorsal to the medial lemniscus (slide 16, slide 17, slide 18 and slide

19). As the central tegmental tract ascends through the rostral pons and into the

midbrain it migrates dorsally to lie on the posterior (dorsal) surface of the red nucleus

just lateral to the medial longitudinal fasciculus. Taste fibers in the central tegmental

tract project to the ventral posteromedial nucleus of the thalamus (slide 29) which,

in turn, sends 3o axons to the postcentral gyrus near the Sylvian fissure (area 43)

[gustatory neocortex] and the insula (see demonstration).

CN X (slides 10-8) -- The vagus nerve contains: 1) the shared contributions from the

nucleus ambiguus (SVE) as previously described [see CN IX above], 2) taste and

general sensation from visceral structures that use the tractus and nucleus solitarius

(SVA, GVA), and 3) general sensation from the region of the external ear (GSA) thatenters the spinal tract of V. In addition, it uniquely contains preganglionic

parasympathetic nerves fibers (GVE) that supply viscera from the head down to the left

colic flexure. These axons arise from the dorsal motor (efferent) nucleus of X. The

rostral extent of this nucleus can be seen on slide 10. Find the tractus and nucleus

solitarius. The clear area dorsomedial to these structures is the dorsal motor

nucleus of X. Now follow this nucleus to its caudal extent (slide 9 and slide 8).

CN XI (slides 6,5) -- The motor nerve fibers innervating the trapezius and

sternocleidomastoid muscles (GSE) arise from a special nucleus located in the upper 5

or 6 cervical spinal segments, called the (spinal) accessory nucleus. This nucleus

can be seen as a lateral extension of the ventral horn on slide 6 and slide 5. On slide

6, observe the rootlets of the spinal accessory nerve lateral to the spinal cord.

CN XII (slides 10-8) -- This nerve contains motor nerve fibers to the intrinsic and

extrinsic muscles of the tongue (GSE). They arise from the hypoglossal nucleus, which

is located adjacent to the dorsal motor nucleus of X throughout its rostrocaudal extent.

On slide 10, locate the dorsal motor nucleus of X. Just ventromedial to thisnucleus is a round gray structure, the hypoglossal nucleus. On slide 9, axons can be

seen arising from the hypoglossal nucleus and traveling ventrally just lateral to the

medial lemniscus to emerge at the preolivary sulcus. Slide 8 shows the caudal

extent of the hypoglossal nucleus and a rootlet of CN XII emerging from the preolivary

sulcus (both sides).









































































50

NEURORADIOLOGY

Slide 61 is an axial (cross sectional) view of an MRI through the pontomedullary

junction, showing CN VI, as well as CN VII and VIII as they emerge from the brainstem

to enter the internal auditory meatus. The cochlea and the semicircular canals can

also be seen. Slide 62 is an axial view of an MRI through the midpons, showing CN V

as it emerges from the middle cerebellar peduncle and traverses the subarachnoid

space to enter into Meckel’s cave.

DEMONSTRATIONS

Whole brain with cranial nerves.

Dorsal view of brainstem showing CN IV.

Half brains showing: Insula and Gustatory Neocortex.

NOTES









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BASAL GANGLIA

Objectives: 1. Know the components of the basal ganglia, their location and their

general “loop” connections as described below and in lecture.

2. Be able to name the discrete motor deficits that occur as a result of

lesions to different regions of the basal ganglia as described in lecture.

Although the term "extrapyramidal system" was introduced by S. A. Wilson over

80 years ago to describe a degenerative disease of part of the basal ganglia and liver

related to copper metabolism, it has never been fully defined. Literally, the

"extrapyramidal system" is all parts of the brain with the exception of the corticobulbar

and corticospinal tracts. However, through the years, many researchers and authors

have used the basal ganglia as a synonym for the extrapyramidal system, since thebasal ganglia serve somatic motor function.

The basal ganglia are a group of functionally and anatomically related subcortical

nuclei. The nomenclature for the basal ganglia can be confusing. As such, the

following breakdown or nuclear groupings of the basal ganglia is presented to help

alleviate some of the confusion.

1. Corpus striatum

A. caudate nucleus

Striatum

B. putamen

Lenticular Nucleus

C. globus pallidus

2. Substantia nigra

3. Subthalamic nucleus

The connections between 1) the nuclei of the basal ganglia and 2) the basal

ganglia and other brain centers are massive and complex. As yet, we do not know the

functional significance of each individual pathway or connection. Consequently, it

serves no useful purpose to elaborate each of them. Instead, we will condense them

{}



52

into a single, broad based, loop circuit as follows: All areas of the cerebral cortex →

via internal & external capsule → striatum (caudate and putamen) and

subthalamic nucleus → globus pallidus and substantia nigra → VA, VL and DM

nuclei of thalamus → via internal capsule → all areas of cerebral cortex.

Although the basal ganglia per se do not project to the spinal cord, they connect

with structures that do (cortex, red nucleus, RF). Through these connections, the basal

ganglia function to modulate and integrate somatic motor activity. Through its input

from virtually all areas of the cerebral cortex to the striatum and subthalamic nucleus,

and its subsequent output from the substantia nigra and globus pallidus to the thalamus

and back to the cerebral cortex, the basal ganglia act in concert with the cerebellum as

an interface between our sensory and motor systems.

Lesions of the various nuclei of the basal ganglia result in relatively discrete

motor deficits collectively called dyskinesias (abnormal involuntary movements).REMINDER: Don’t forget that you should be able to name the discrete motor deficits

that arise as a result of lesions to different regions of the basal ganglia as described in

lecture.

Horizontal and Coronal Sections

Corpus Striatum (caudate, putamen and globus pallidus) and substantia nigra --

The caudate nucleus forms an incomplete ring around the dorsolateral and ventrolateral

aspect of the thalamus and is divided into three parts: head, body and tail. The large

head is located rostral to the thalamus, the body along the dorsolateral aspect of the

thalamus and the tail curves ventrolaterally to reside in the roof of the inferior horn of the

lateral ventricle. The tail terminates at the amygdaloid nucleus. The putamen and

globus pallidus reside in the concavity of the caudate nucleus, with the putamen located

lateral to the globus pallidus (see Fig. 5 on next page). The substantia nigra is located

in the midbrain tegmentum just dorsomedial to the cerebral peduncles. The

subthalamic nucleus lies ventral to the thalamus at the junction of the midbrain and

diencephalon (this structure will be seen on slides).



53

On your coronally sliced brain specimen, select a section just rostral to the

anterior commissure. The nuclear mass forming the lateral wall of the lateral ventricles

is the head of the caudate nucleus. Just ventrolateral to the anterior limb of the

internal capsule is the putamen. On the next section caudally, the head of the caudatenucleus remains in the same position if the thalamus is not present. However, the

putamen is typically joined medially at this level by the globus pallidus. The next

section caudally should contain the thalamus. If so, the head of the caudate nucleus

has been replaced by the body of the caudate nucleus. If the hippocampal formation

can be seen in the inferior horn of the lateral ventricle in the temporal lobe, find the

small tail of the caudate nucleus in the roof of the inferior horn of the lateral ventricle.

Follow and identify the body and tail of the caudate nucleus, putamen and globus

pallidus in subsequent sections. On some of your specimens, the coronal cuts may

go far enough caudal that the midbrain has been cut in frontal section. If so, try to find a

black pigmented region in the midbrain tegmentum. This is the substantia nigra.

What causes the black pigmentation of this region?

Select a horizontal section just ventral to the body of the corpus callosum.

(NOTE: As you go through your horizontal sections, correlate and compare what you



54

see with the same structures in the coronal sections. This will help you get a better

understanding of the 3-dimensional anatomy of the basal ganglia). Identify the head

and body of the caudate nucleus on this section, if possible. On more ventral

sections, identify the head and tail of the caudate nucleus, putamen and globus

pallidus. As you view more ventral sections, you may be able to observe the head of

the caudate nucleus fuse with the putamen at the rostral extent of the anterior limb of

the internal capsule. In addition, if the most ventral cut goes through the midbrain, the

substantia nigra can be seen as a black pigmented region just dorsomedial to the

cerebral peduncles. If your specimen does not show this, look on your neighbor's

specimen and/or look at the demonstrations.

Slide Set

Begin with slide 21. The substantia nigra can be seen at this and all midbrain

levels as a pale nuclear region dorsomedial to the cerebral peduncles. Follow the

substantia nigra rostrally (slide 22, slide 23, slide 24, slide 25, slide 26 and slide 28).

Lesioning the substantia nigra produces what clinical malady? Note the body and tail

of the caudate nucleus in slide 26 and slide 28, and a close-up of the tail of the

caudate nucleus in the roof of the inferior horn of the lateral ventricle on slide 27.

As the transition zone between the midbrain and diencephalon is reached (slide

25, slide 29, slide 30 and slide 31), the subthalamic nuclei appear dorsal to the

substantia nigra as fusiform tapered structures resembling cat's eyes. A lesion of the

right subthalamic nucleus would produce what SPECIFIC clinical symptom(s)? On

slide 31, two of the output pathways from the globus pallidus to the thalamus can be

seen. The thin dark line of fibers on the dorsal surface of the subthalamic nucleus on

the right side is the lenticular fasciculus. Near its medial extent, the fibers of the

lenticular fasciculus arch dorsolaterally (not easily seen here) to join the large bundle of

nerve fibers just dorsal to the lenticular fasciculus, called the thalamic fasciculus. The

thalamic fasciculus contains axons from the cerebellum, globus pallidus (via the

lenticular fasciculus and ansa lenticularis) and the substantia nigra, that are destined forthe VA, VL and DM nuclei of the thalamus. Also find the putamen and body of the

caudate nucleus on this slide and note the relationship between the globus pallidus

and internal capsule.

Slide 32 (left side) and slide 33 (right side) show the prominent ansa

lenticularis as it arises from, and travels ventral to, the medial segment of the globus


























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pallidus. As it passes medial to the globus pallidus, it arches dorsally to join the

thalamic fasciculus (not shown in these slides).

On slide 33 and subsequent slides (slide 34, slide 35, slide 36, slide 37 and

slide 38), identify the caudate nucleus, globus pallidus and the putamen, where

possible. Slide 35 shows the fusion of the head of the caudate nucleus and

putamen at the rostral extent of the anterior limb of the internal capsule.

NEURORADIOLOGY

Slide 47 and slide 48 show the head of the caudate nucleus and the

putamen. In addition to the above structures, slide 49 also shows the globus

pallidus. Slide 50 reveals the substantia nigra (NOTE THE ORIENTATION OF THE

MIDBRAIN).

DEMONSTRATIONS

Caudate nucleus.

Amygdala.

NOTES



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CEREBELLUM

Objectives: 1. Understand the gross anatomy of the cerebellum and its positional

relationship to the cerebrum and brainstem.

2. Understand the functions of the cerebellum as described here and in

lecture.

3. Know and understand the functional/clinical consequences of

cerebellar lesions.

The cerebellum (L. little brain) straddles the dorsal aspect of the brainstem.

Within the skull, it resides in the posterior cranial fossa immediately inferior to the

tentorium cerebelli. It is attached to the brainstem by three paired nerve fiber bundles

called cerebellar peduncles. It is through these peduncles that the cerebellum

communicates and interacts with other regions of the CNS. By way of these

connections, the cerebellum has a profound effect on equilibrium, posture, muscle tone

and the coordinated, synergistic muscle contractions required for the meaningful

execution of a variety of tasks including walking, speech, eye movements, writing,

playing musical instruments, etc. The role of the cerebellum is not to initiate these

movements per se, but to insure that these movements, when initiated, are smooth,

purposeful and coordinated. NOTE: Voluntary movements (via corticospinal and/or

corticobulbar tracts) can be made without cerebellar involvement, but the result is

clumsy, disorganized movement (dyssynergia/cerebellar ataxia).

GROSS ANATOMY – Whole and Half Brains

On your whole brains, observe the cerebellum from the dorsal (posterior) side.

The superior surface of the cerebellum is flattened and tucked beneath the occipital

lobes of the cerebral hemispheres. Gently separate the cerebellum and occipital lobes

to view the superior surface of the cerebellum. The midline vermis is elevated on

the superior surface with the cerebellar hemispheres gently sloping laterally. Near the

middle of the superior surface of the cerebellum is a transverse crease called the

primary fissure. It is best seen on demonstration or on your half brains. This fissure

divides the cerebellum into anterior and posterior lobes. Do not confuse this fissure with

the horizontal fissure which runs along, or just inferior to, the lip of cerebellum that

separates the superior and inferior surfaces. Note the blood vessels ramifying on the



57

superior surface. These are branches of the superior cerebellar arteries and their

corresponding veins.

In contrast to the superior surface, the inferior surface of the hemispheres is

convex. The midline vermis is depressed and hidden from view, forming the floor of a

deep crevice, the posterior median fissure. The falx cerebelli resides in this fissure

when the brain is in the skull. Near the midline inferiorly, the cerebellum surrounds the

dorsolateral aspect of the medulla with two swellings, the cerebellar tonsils.

Occasionally, the cerebellar tonsils are useful in diagnosing elevated intracranial

pressure, since they tend to herniate through the foramen magnum as a result of this

condition. Two named blood vessels supply the inferior surface of the cerebellum.

Their origin and distribution can be highly variable and considerable overlap of

territories is not uncommon. Their typical distribution is described here. The posterior

inferior cerebellar arteries typically arise from the vertebral arteries. They archdorsally around the medulla, giving off small branches to the lateral medullary

region, then continue to ramify on the inferior surface of the cerebellum posterior to the

tonsils. The anterior inferior cerebellar arteries typically arise from the basilar artery

to pass laterally over the cerebellopontine angle and ramify on the inferior surface of

the cerebellum anterior to the tonsils. Just lateral to the cerebellopontine angle is a

slender lateral projection of cerebellar tissue, the flocculus (part of the flocculonodular

lobe). A fissure extends laterally from the posterior aspect of the flocculus. This is the

posterolateral fissure, which separates the flocculonodular lobe from the posterior

lobe.

Two of the three cerebellar peduncles can be seen on the ventral surface of your

whole brain specimens. The large middle cerebellar peduncle (brachium pontis) lies

rostral to the flocculus. Medial to the flocculus, find the inferior olive and postolivary

sulcus. The rounded mass dorsal to the postolivary sulcus is the inferior cerebellar

peduncle (restiform body). The above two peduncles transmit primarily afferent nerve

fibers to the cerebellum.



58

Now look at the medial surface of your half brain specimen (see Fig. 6 below).

The cut was made through the midline, bisecting the vermis.

The cut surface of the cerebellum has the appearance of trees with leaves

sprouting along the extent of their branches. Each one of these "leaves" is called a

folium (pl. folia). Like the cerebral cortex, the neurons of the cerebellar cortex lie at

the surface in the folia. Close inspection reveals "branches" of white matter converging

in the deeper regions of the cerebellum to form "trunks." The bases of the trunks merge

to form the deep white matter that constitutes the roof of the fourth ventricle.

Imbedded in this deep white matter are the deep cerebellar nuclei (to be seen on

slides). The cerebellar cortex at the vermis is separated into nine lobules, based

roughly on the "tree" analogy as described above (i.e. each "tree" is approximately

equal to one lobule). We will learn only those lobules bordering the primary and

posterolateral fissures. Find the culmen and the declive along the superior surface of

the vermis. The deep groove between these two lobules is the primary fissure, which

separates the anterior and posterior lobes. Being careful not to tear any tissue, follow

this fissure onto the superior surface of the cerebellum. Now find the nodule (the

central part of the flocculonodular lobe) and the uvula along the inferior surface of thevermis. The groove between these two lobules is the posterolateral fissure. Note the

cerebellar tonsil just inferior and lateral to the uvula.

Now find the superior medullary velum, which forms the roof of the fourth

ventricle at this level. The relatively thick wall of the fourth ventricle at this level is



59

formed by the superior cerebellar peduncle (brachium conjunctivum). This

peduncle is the primary pathway for efferents from the cerebellum.

Functional subdivisions of the cerebellum -- Now that you have some knowledge of the

gross anatomy of the cerebellum, we can separate it into its functional subdivisions.

1. Vestibulocerebellum (archicerebellum) -- consists of the flocculonodular

lobe, which has extensive connections with the vestibular system within the

brainstem.

FUNCTION: EQUILIBRIUM, REGULATION OF EYE MOVEMENT

2. Spinocerebellum (paleocerebellum) -- consists roughly of the vermis and

paravermal zones (just lateral to the vermal region), including the tonsil.

This part of the cerebellum receives proprioceptive information from the body

(spinal cord) and head (brainstem).

FUNCTION: MUSCLE TONE, STEREOTYPIC MOTOR ACTIVITY…

(WALKING, STANDING, SWIMMING, ETC.)

3. Pontocerebellum (neocerebellum; cerebrocerebellum) -- consists of the

lateral hemispheric zones. This part of the cerebellum has major

connections with the cerebral cortex via brainstem nuclei.

FUNCTION: MOTOR COORDINATION OF NON-STEREOTYPED(LEARNED, SKILLED) MOVEMENTS

AFFERENT AND EFFERENT CONNECTIONS – Slide Set

There are a number of afferent and efferent pathways for the cerebellum. To list

and/or discuss all of them would serve no useful purpose. Instead, we will concentrate

on those pathways that can readily be assigned a function that will help in

understanding how the cerebellum works through its interconnections with other regions

of the CNS.

Afferent Connections -- The cerebellum receives afferents from the spinal cord and

brainstem. These afferents will be studied in an ascending fashion, beginning with the

spinal cord.



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1. Spinal cord -- In contrast to the dorsal column and spinal lemniscus

pathways which transmit conscious information, spinal cord pathways to

the cerebellum transmit the unconscious modalities of proprioception,

touch and pressure impulses to the vermal and paravermal regions of

the cerebellum. They do so by ascending along the superficial surfaces of

the lateral funiculi of the spinal cord and enter the cerebellum primarily

through the inferior cerebellar peduncle. We will not be concerned with

naming or following these pathways on slides.

2. Brainstem -- Brainstem afferents arise primarily from three sources:

A) pontine nuclei, B) vestibular nuclei and C) inferior olivary nuclei.

A. (Cortico)-ponto-cerebellar pathway -- Axons from the cerebral cortex

project to the ipsilateral pontine nuclei via the cerebral peduncles. The

pontine nuclei then project their axons to the contralateral cerebellar

cortex (lateral region of posterior lobe) via the middle cerebellar peduncle.

B. Vestibulocerebellar tract -- From the vestibular nuclei via the

juxtarestiform body to the flocculonodular lobe.

C. (Cortico)-olivo-cerebellar pathway -- Axons from the cerebral cortex

project to the inferior olivary nucleus (complex). Cells in the inferior olivary

complex then project axons contralaterally to all areas of the cerebellar

cortex via the inferior cerebellar peduncle. NOTE: In addition to cortical

input, the inferior olivary complex also receives afferents from the red

nucleus, basal ganglia, RF and spinal cord.

Begin with slide 19. The cerebral cortex provides axons to the ventral pontine

nuclei via the cerebral peduncles. The pontine nuclei within the ventral pons give riseto axons that cross the midline as the pontocerebellar pathway (transverse pontine

fibers). These can be seen as horizontal blue streaks within the ventral pons. These

axons gain access to the cerebellum via the large middle cerebellar peduncle to

terminate in the lateral hemispheres of the posterior lobe. Identify the above structures

on slide 18, slide 17 and slide 16.



















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There are four pairs of vestibular nuclei (to be studied shortly) within the medulla

and pons. These nuclei provide afferent fibers to the flocculonodular lobe of the

cerebellum via the juxtarestiform body. As the name implies, this relatively small

pathway to the cerebellum lies in juxtaposition (medial) to the restiform body (inferior

cerebellar peduncle), and can be seen on slide 17, slide 16, slide 15 and slide 14.

(It should also be noted that this pathway carries efferent fibers from the cerebellum to

the vestibular nuclei).

The inferior olivary nucleus (slides 15-12,10,9) projects axons to the cerebellum

via the contralateral inferior cerebellar peduncle. Begin with slide 15, which is at the

level of the medullary-pontine junction and observe the following: The left and right

inferior olivary nuclei each project their axons to the contralateral cerebellar cortex by

sending them medially to decussate through the medial lemniscus and continue

through the contralateral inferior olivary nucleus to arch dorsolaterally where theyenter the contralateral inferior cerebellar peduncle. This can be seen clearly on slide

13 and slide 12. These afferents to the cerebellum from the inferior olivary nuclei go

directly to Purkinje cells and are collectively called climbing fibers.

Efferent Connections -- Although the afferent connections/pathways to the cerebellum

are important, they are relatively diffuse from an anatomical standpoint. In contrast, the

vast majority of axons exit the cerebellum via the superior cerebellar peduncle

(exception: juxtarestiform body). To understand this concept, consider that the input to

the cerebellum comes from a wide variety of structures and travels to all regions of the

cerebellar cortex via three peduncles. The output from the cerebellar cortex (Purkinje

cells) is also diffuse. However, the vast majority of these cells do not project their axons

outside the confines of the cerebellum, but instead send them to converge and synapse

on the four pairs of deep cerebellar nuclei, which are located within the white matter in

the roof of the fourth ventricle. This relatively compact set of nuclei gives rise to axons

that pass primarily through the superior cerebellar peduncle. Because of this compact

anatomical arrangement, small lesions to this region (deep cerebellar nuclei, sup.

cerebellar peduncle) can produce profound effects.

Deep cerebellar nuclei (slides 10,11,13,14) -- Look at slide 10. The deep

cerebellar nuclei are located within the deep white matter of the cerebellum

overriding the caudal pons and medulla. They are, from lateral to medial:


































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1. dentate nucleus -- receives afferents from the Purkinje cells of the lateral

hemispheres.

2. emboliform nucleus

nucleus interpositus; receives afferents fromthe Purkinje cells of the paravermal region.

3. globose nucleus

4. fastigial nucleus -- receives afferents from the Purkinje cells of the vermis

and flocculonodular lobe.

Now find the above nuclei on slide 11, slide 13 and slide 14. The fastigial

nucleus projects its axons to vestibular nuclei via the juxtarestiform body. Axons from

the remaining deep cerebellar nuclei exit the cerebellum via the superior cerebellar

peduncle (slide 16 and slide 19). Slide 20 and slide 21 illustrate how the superior

cerebellar peduncle arches ventromedially to decussate (decussation of the superior

cerebellar peduncle) at the levels of the rostral pons and caudal midbrain. After

decussating, these axons pass through the contralateral red nucleus (slide 22, slide

23, slide 24, slide 25). Some of these axons terminate in the red nucleus which, in

turn, gives rise to axons that decussate immediately and descend to the spinal cord as

the rubrospinal tract. This pathway can be seen as rounded projections from the

ventral surface of the decussation of the superior cerebellar peduncle on slide 21. Therubrospinal tract provides excitatory motor innervation primarily to the flexor muscles of

the upper extremity.

Other axons from the deep cerebellar nuclei pass through the red nucleus and

ascend to terminate in the ventrolateral (VL) nucleus of the thalamus (slide 31 and

slide 32). The VL gives rise to axons that project to the cerebral cortex (Brodmann's

areas 4 and 6). This pathway provides information to the cerebral cortex concerning the

location of the body in space to ensure smooth coordinated movements. Thus, the

cerebral cortex forms loop circuits with the cerebellum as follows: cerebral cortex →

via int. capsule & cerebral peduncles → pontine & inf. olivary nuclei → via middle

& inf. cerebellar peduncles → cerebellum → via sup. cerebellar peduncle → VL of

thalamus → via int. capsule → cerebral cortex. Can you recall a pathway or

pathways involving the basal ganglia that are similar or have common elements to those

of the cerebellum?

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Cerebellar Pathology -- There are 4 important concepts to keep in mind when

considering lesions of the cerebellum. These concepts are as follows:

1. Lesions of the cerebellum or its afferent or efferent pathways may disrupt

normal coordinated movements, but will not cause paralysis.

2. Each cerebellar hemisphere exerts its influence on the muscles of the

ipsilateral side of the body. Can you justify this statement anatomically?

3. The flocculonodular lobe influences the axial musculature bilaterally.

4. Lesions of the efferent pathway (deep nuclei and/or superior cerebellar

peduncles) produce more profound and permanent deficits than do lesions of

the afferent pathways or cerebellar cortex.

NEURORADIOLOGY

On slide 45, find the culmen, declive, primary fissure and superior (anterior)

medullary velum. On slide 46, identify the middle and superior cerebellar

peduncles. Slide 54 and slide 55 show cerebellar pathology. What lobe(s) of the

cerebellum is (are) involved? What artery provides the major blood supply to the region

of the cerebellar pathology? On slide 60, find the cerebellar tonsils and the inferior

cerebellar peduncles. Slide 61 shows the cerebellar vermis. On slide 62, find CN V

emerging from the middle cerebellar peduncle. On slide 63, both the middle and

superior cerebellar peduncles can be seen.

DEMONSTRATIONS

Cerebellum -- cerebellar peduncles, cerebellar fissures (primary, horizontal,

posterolateral), flocculus, nodule.

NOTES






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VESTIBULAR SYSTEM

Objectives: 1. Find and identify the vestibular nuclei and understand the functional

significance of their connections with extraocular nuclei, cerebellum

and spinal cord.

2. Understand how the vestibular system is tested and the normal

behavioral consequences of the testing procedures.

CN VIII (vestibulocochlear nerve) -- As the name implies, the vestibulocochlear

nerve has two primary functions: equilibrium (vestibular portion) and hearing (cochlear

portion). As such, each division of this nerve has discrete external structures as well as

discrete internal nuclei and pathways within the brainstem that serve each of these

modalities. In this laboratory session, we will identify the central nuclei and pathwaysthat serve the vestibular division of CN VIII.

Peripherally, hair cells within the ampullae of the semicircular canals, utricle and

sacculus are connected with the peripheral processes of the primary vestibular

afferents. The cell bodies for these primary afferents are located in the vestibular

(Scarpa's) ganglion, which resides in the internal auditory meatus. A few of the central

processes of these ganglion cells project directly to the flocculonodular lobe via the

juxtarestiform body. However, the vast majority of these central processes project to

the ipsilateral vestibular nuclei located in the pons and medulla. The vestibular nuclei

give rise to axons that project to spinal cord, cerebellum, extraocular motor nuclei, RF,

contralateral vestibular nuclei and thalamus (small nucleus between VPM and VPL).

Efferents from the vestibular nuclei to the thalamus are relayed to the postcentral and

superior temporal gyri. These projections from the vestibular nuclei to the thalamus and

on to the cerebral cortex are thought to ascend via the brainstem reticular formation or

possibly with ascending auditory fibers to provide cortical awareness of equilibrium.

Vestibular division of CN VIII (slides 18-12,10) -- Beginning with slide 15, locate

the inferior cerebellar peduncle. The "salt and pepper" or speckled regiondorsomedial to the inferior cerebellar peduncle identifies the inferior (spinal)

vestibular nucleus. Medial to the inferior vestibular nucleus lies the medial vestibular

nucleus. Notice on the left side how the fibers of the juxtarestiform body intermingle

with medial and inferior vestibular nuclei. Identify the medial longitudinal fasciculus

(MLF) in the midline at the floor of the fourth ventricle. At this level, the MLF contains:







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1) ascending axons from the vestibular nuclei to the extraocular motor nuclei (CN III, IV,

VI) for coordinating eye movements during the process of maintaining equilibrium, and

2) descending bilateral axons from the medial vestibular nuclei for control of somatic

muscles in maintaining equilibrium. The MLF continues inferiorly into the cervical spinal

cord as the medial vestibulospinal tract. Identify, where possible, the above structures

on slide 14, slide 13, slide 12 and slide 10.

Now return to slide 15 and reorient yourselves. Find the inferior vestibular

nucleus. On subsequent rostral slides, this nucleus is replaced by the lateral

vestibular nucleus. The slender dorsolateral extension of gray matter from the lateral

vestibular nucleus is the caudal extent of the superior vestibular nucleus.

Using your brain atlas and slide 16, slide 17 and slide 18, follow the MLF and

the medial, lateral and superior vestibular nuclei rostrally to get a feel for their

location and rostrocaudal extent. As you proceed, also observe the juxtarestiformbody on slide 16. Note that the lateral and medial vestibular nuclei do not extend into

the upper 1/2 of the pons (slide 18). How far rostrally would you expect to find the

MLF, and why?

NEURORADIOLOGY

On slide 61, find CN VII & VIII emerging from the cerebellopontine angle. Also

find the internal auditory meatus and the semicircular canals.

NOTES













































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AUDITORY SYSTEM

Objectives: 1. Understand the anatomy and function of the central and peripheral

structures that comprise the auditory system.

2. Know and understand the differences in symptoms between central

and peripheral lesions of the auditory system.

Auditory information is transmitted to the CNS via the auditory division of CN VIII

(vestibulocochlear nerve). Peripherally, hair cells within the cochlea are in synaptic

contact with the peripheral processes of the spiral ganglion cells, which are located in

the bony modiolus. The central processes of these cells form the cochlear division of

CN VIII.

Observe slide 40. This is a cross section through the cochlea. The large spaceat the top of the slide is the scala vestibuli (contains perilymph). The diagonal

membrane is called the vestibular (Reissner's) membrane. This structure separates

the scala vestibuli and the scala media (cochlear duct). The latter contains

endolymph. The cavity at the bottom of the slide is the scala tympani which is

continuous with the scala vestibuli at the apex of the cochlea. As such, it contains

perilymph. The large structure on the left (modiolus) forms a shelf-like process called

the bony spiral lamina. At the tip of the shelf, the basilar membrane stretches to the

right to make contact with the spiral ligament which attaches to the outer region of the

bony labyrinth (not seen). Resting on the basilar membrane is the (spiral) organ of

Corti. Above the basilar membrane at approximately its midpoint, a row of three

slender cells can be seen. These are the outer hair cells. Just to the left of these cells

is the fusiform space called the space of Nuel. The space just to the left of the space

of Nuel is the (inner) tunnel of Corti, which is bounded on the left and right by the

inner and outer columns respectively. The inner hair cells reside at the tip of the

inner column. In this plane of section, there are typically one row of inner hair cells and

3 rows of outer hair cells. The next space to the left is the internal spiral sulcus. The

roof of this sulcus is formed by the translucent tectorial membrane, which extends tothe right to make contact with the apical hairs of the inner and outer hair cells. The hair

cells are in contact with the peripheral processes of the spiral ganglion cells, which

gain access to the hair cells via the bony spiral lamina. The spiral ganglion resides in

the modiolus and contains the primary afferent cell bodies in the auditory pathway.

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Vibration of the foot of the stapes on the oval window creates displacement of the

basilar membrane. This phenomenon produces a shearing effect between the tectorial

membrane and the hair cells. When the hairs are displaced because of the shearing

forces, the hair cells stimulate the spiral ganglion to transmit impulses into the CNS via

the auditory division of CN VIII.

As a point of interest, there is tonotopic organization within the cochlea. That is,

higher frequencies result in displacement of the basilar membrane at the base of the

cochlea, with lower frequencies displacing the basilar membrane toward the apex of the

cochlea. This marks the beginning of a continuous tonotopic arrangement of cells and

nerve fibers, both peripheral and central, throughout the auditory pathway.

The central auditory pathways can be seen on slide 28 and slides 26 -12. Begin

with slide 15. On the right side, just lateral to the inferior cerebellar peduncle, there

is a large region of mottled gray matter, the ventral cochlear nucleus. Immediatelyventral to this nucleus is the darkly stained region of CN VIII as it emerges from the

cerebellopontine angle. The clear nuclear area along the dorsal aspect of the inferior

cerebellar peduncle is the dorsal cochlear nucleus. Identify, where possible, the

above structures on slide 14, slide 13 and slide 12.

Now follow the auditory pathway as it ascends through the brainstem. Beginning

with slide 15, note the ventral cochlear nucleus and CN VIII on the right side. The

dorsal and ventral cochlear nuclei contain the 2o auditory neurons. Although the

cochlear nuclei project some of their axons ipsilaterally, the majority cross the midline

via the trapezoid body, which is the small bundle of vertically arranged axons located

in the midline between the two medial lemnisci. Some of the crossed fibers of the

ventral cochlear nucleus synapse in the contralateral superior olivary nucleus

(SOLN), which can be seen on slide 16. This nucleus is located just lateral to the

central tegmental tract and is shaped like an inverted "V". The majority of axons

arising from the SOLN enter the ipsilateral lateral lemniscus, which lies just lateral to

the SOLN, where they join the ascending fibers of ipsilateral and contralateral cochlear

nuclei. NOTE: In addition to ascending fibers, some axons from the SOLN project to

the motor nuclei of CN V and VII, others project to the motor nuclei of CN III, IV, VI andthe RF. Can you speculate why these connections would be present? Find the SOLN,

lateral lemniscus and trapezoid body in slide 17. Since the SOLN is found only in

the caudal 1/3 of the pons, it will not be seen in slide 18 and subsequent slides. Follow

the lateral lemniscus rostrally as it fans out to assume a vertical orientation in the lateral

wall of the rostral pons (slide 19 and slide 20). On slide 20, the lateral lemniscus is












































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split into medial and lateral portions by the nucleus of the lateral lemniscus, another

relay nucleus in the auditory pathway. On slide 21, the nerve fibers of the lateral

lemniscus can be seen sweeping medially to enter the ventrolateral aspect of the

nucleus of the inferior colliculus where they synapse. Axons arising from the

nucleus of the inferior colliculus emerge from the dorsolateral aspect of the nucleus to

ascend along the lateral wall of the rostral midbrain as the brachium of the inferior

colliculus (slide 22). Follow the brachium of the inferior colliculus rostrally as it

enters and synapses within the ipsilateral medial geniculate (body) (slide 23, slide

24, slide 25, slide 26 and slide 28). Axons arising from the medial geniculate body

project to the dorsal aspect of the superior temporal gyrus called the transverse

temporal gyrus (of Heschl) (Brodmann's areas 41,42). NOTE: THIS CAN BE SEEN

ON DEMONSTRATION.

Given the external and internal anatomy of the auditory system, would a unilateral lesion of the lateral lemniscus in the midbrain produce ipsilateral loss of

hearing? If not, what symptom(s) would you expect from this lesion and why? Where

would you lesion the auditory pathway to achieve total loss of hearing in the left ear?

NEURORADIOLOGY

On slide 61, find CN VII & VIII, the internal auditory meatus and the cochlea.

DEMONSTRATIONS

Half brain showing: Auditory cortex.

Dorsal view of brainstem showing: inferior colliculus, brachium of inferior

colliculus, medial geniculate.

NOTES
































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DIENCEPHALON

In this laboratory session, we will study the hypothalamus, a subdivision of the

diencephalon (L. interbrain ). However, for the sake of completeness, the subdivisions

of the diencephalon are listed below:

A. Epithalamus -- consists of:

1. Habenular nuclei and their connections to be studied with the

2. Pineal Gland limbic system

B. Subthalamus -- consists of:

1. sensory fasciculi

2. rostral extensions of midbrain nuclei previously studied with3. efferent fiber bundles from cerebellum & the basal ganglia

globus pallidus (part of basal ganglia)

C. Thalamus -- The thalamus is, by far, the largest component of the

diencephalon. We have studied the various nuclei of the thalamus and its

relationship to surrounding structures in our journey through the CNS thus far.

As such, we will not have a separate laboratory on this structure. However, it

would serve you well to consider the following: The two thalami lie interposed

between 1) the cerebral cortex, 2) basal ganglia, 3) brain stem centers, and 4)

spinal cord. Consequently, each thalamus is intimately associated with: 1)

the sensory systems, by processing and relaying sensory information to the

cerebral cortex, 2) the motor systems, particularly with the motor cortex,

cerebellum and basal ganglia, and 3) the limbic system (to be studied

shortly), which controls emotion, motivation, learning & memory and sexual

behavior. Moreover, the thalamus has reciprocal connections with virtually all

areas of the cerebral cortex. When one considers these extensive

interconnections between the thalamus and a variety of major motor, sensoryand behavioral components of the CNS, it becomes apparent that the

thalamus is far more than a relay station for sensory pathways.

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D. HYPOTHALAMUS

Objectives: 1. Learn the gross and macroscopic anatomy of the hypothalamus.

2. Learn the major afferent and efferent pathways of the hypothalamus.

3. Understand the major functions of the hypothalamus as given here and

in lecture.

Physically, the hypothalamus is a relatively small part of the diencephalon.

However, its small size is not an indicator of the importance of this structure. From a

functional standpoint, the hypothalamus is a central figure in the regulation of a broad

range of bodily functions. Through its endocrine connections via the pituitary gland, and

its widespread nerve fiber connections with a wide variety of other brain regions and

spinal cord, it regulates endocrine, autonomic, emotional and somatic activity.

1. Endocrine system

A. Direct regulation occurs through the supraopticohypophyseal tract

(contains axons from the supraoptic and paraventricular nuclei of the

hypothalamus) which releases hormones (oxytocin and vasopressin)

into the capillaries of the general systemic circulation within the

posterior lobe of the pituitary.

B. Indirect regulation occurs through the tuberohypophyseal tract, which

delivers "releasing" and "inhibiting" factors to sinusoids in the

infundibulum. These factors then gain access to the anterior lobe via

the blood vessels of the hypophyseal portal system where they

stimulate or inhibit the release of a variety of hormones, such as

prolactin, ACTH, LH and others, into the systemic circulation.

2. Autonomic nervous system

The hypothalamus is involved in the expression of both parasympathetic

(anteromedial hypothalamus) and sympathetic (posterolateral

hypothalamus) functions. Hence, it is often referred to as the "head

ganglion of the autonomic nervous system". Consequently, the



71

hypothalamus regulates basic physiologic functions such as temperature

regulation, heart rate, blood pressure and gastrointestinal activity. For

example, the hypothalamus monitors blood temperature, producing both

visceral (blood vessel constriction) and somatic activity (shivering) if the

temperature of the blood circulating through the hypothalamus should

drop. In addition, through its connections with the limbic system, the

hypothalamus regulates emotion-based behavior such as anger, rage and

sexual activity. To produce these global effects, the hypothalamus has

extensive influence via the endocrine system and through synaptic

connections within the CNS, including telencephalon, brainstem and

spinal cord.

Although experimental and clinical evidence indicate that specific regions of thehypothalamus, when lesioned, produce specific deficits or behavioral abnormalities, it

cannot be said with absolute certainty that the hypothalamus is solely responsible for a

given function. For example, there is an important pathway, the medial forebrain

bundle, which travels rostrocaudally in the lateral region of the hypothalamus and

interconnects a variety of forebrain and midbrain structures with the hypothalamus.

Consequently, should the lateral region of the hypothalamus be lesioned, it would

include the medial forebrain bundle. As a result, this pathway must be considered as a

possible source of the resulting clinical symptom(s).


On the ventral surface of your whole brain specimens, find the optic nerves (CN

II). Gently elevate them and attempt to see the lamina terminalis, which forms both

the rostral wall of the 3rd ventricle and the rostral boundary of the hypothalamus.

Immediately caudal to the optic chiasm, the infundibulum can be seen. This structure

connects the hypothalamus with the pituitary (hypophysis). The region of the

hypothalamus between the infundibulum and the mammillary bodies is the tubercinereum. The rounded swellings of the mammillary bodies form the caudalmost

extent of the hypothalamus and reveal the location of the underlying mammillary nuclei.

On the medial surface of your half brain specimens, find the lamina terminalis,

optic chiasm, tuber cinereum and mammillary body. The midline region

immediately dorsal to the optic chiasm, tuber cinereum and mammillary body is the 3rd



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ventricle. The wall of the 3rd ventricle from this level dorsally to the hypothalamic

sulcus is formed by the hypothalamus. Note how the optic chiasm fuses with the

ventral portion of the hypothalamus. It is at this point that axons from the ganglion cells

of the retina enter the hypothalamus to provide regulation of diurnal rhythms.

The hypothalamus can be roughly divided into four regions from rostral to caudal:

1. preoptic area -- the region immediately rostral to the optic chiasm.

2. supraoptic (anterior) region -- the area immediately dorsal to the optic

chiasm.

3. tuberal region -- the tuber cinereum and the area dorsal to it.

4. mammillary (posterior) region -- the region of the mammillary bodies andthe area dorsal to them.

Slide Set

The hypothalamus has many afferent and efferent connections associated with

the limbic system (to be covered later in this laboratory session). In this portion of the

laboratory, we will study the anatomy of the hypothalamus per se and the important

pathways to and from the brainstem and spinal cord.

Begin with slide 9. The central tegmental tract is sandwiched between the

inferior olivary nucleus and the spinal lemniscus. This pathway carries nerve fibers from

a variety of sources, including cortical and basal ganglia input to the brainstem reticular

formation (RF), efferent fibers from red nucleus to inferior olive and visceral (taste)

information from the nucleus solitarius to the hypothalamus. Taste fibers peel off from

the central tegmental tract to terminate in the hypothalamus. The hypothalamus, in

turn, sends descending fibers to the brainstem and spinal cord. This combined

ascending/descending pathway provides an autonomic response (salivation, sweating,

vomiting) to the tastes that are being experienced. Follow the central tegmental tract rostrally through the medulla and pons (slide 10, slide 12, slide 13, slide 14, slide 15,

slide 16, slide 17, slide 18). Through these regions, the central tegmental tract resides

on the dorsal aspect of the medial lemniscus as the latter assumes a horizontal position

in the pons. The dorsal longitudinal fasciculus (DLF) maintains a relatively constant

position at the floor of the 4th ventricle throughout the brainstem and can be best seen





































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on slide 14 (bilaterally) and slide 15 (right side). This important (primarily) efferent

pathway from the hypothalamus synapses on: 1) brainstem RF, 2) brainstem nuclei

involved with eating, swallowing, vomiting, salivation and digestion and 3) enters the

spinal cord in the lateral funiculus to synapse on cells of the intermediolateral cell

column.

The various regions of the hypothalamus can be seen on slides 24, 25, 29-33, 38

and 39. Begin with slide 24 and slide 25, which reveal the mammillary bodies and

part of the tuberal region of the hypothalamus in horizontal section. Slide 29, slide

30 and slide 31 also show the mammillary bodies. Slide 32 is an oblique section

through the tuberal region of the hypothalamus. The tuberal region is flanked by the

optic tracts. The 3rd ventricle can be seen in the midline. Note the hypothalamic

sulcus delineating the dorsal extent of the hypothalamus. The large, compact fascicle

of axons within the tuberal region is the fornix. This important pathway to thehypothalamus will be discussed in detail as part of the limbic system. At this point, it is

an important landmark that separates the medial and lateral regions of the

hypothalamus. The diffuse gray colored area immediately lateral to the fornix is the

medial forebrain bundle as it travels through the scattered cells of the lateral nucleus

of the hypothalamus. Slide 33 is an oblique section through the infundibulum and

rostral tuberal region. On slide 33, identify the 3rd ventricle, fornix, medial and

lateral nuclear regions, medial forebrain bundle and the optic tracts.

Slide 38 is a relatively high power view of a coronal section through the anterior

commissure and anterior region of the hypothalamus. Unlike the other brain

sections in your slide set, this region is stained with a cellular stain. As such, the nuclei

(cell bodies) will stain darkly with the fiber tracts appearing unstained. Find the 3rd

ventricle. The rounded dark areas within the walls of the 3rd ventricle are the

paraventricular nuclei. The dorsal aspect of the optic chiasm can be seen as it fuses

with the hypothalamus ventrally. The darkly stained region in the lateral concavity

between the optic chiasm and the hypothalamus on each side are the supraoptic

nuclei. What neurotransmitter(s) is (are) secreted by the cells of the paraventricular

and supraoptic nuclei? Can you find the septum pellucidum , lateral ventricles and internal capsule ? What part of the internal capsule is seen here?

Slide 39 is a sagittal section of the brainstem. Is this a midsagittal section? Can

you defend your answer based on sound anatomical evidence? Identify the

mammillary, tuberal and anterior regions of the hypothalamus. Also find the optic

nerve, optic chiasm, anterior commissure and fornix within the hypothalamus.

























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Arising from the dorsal aspect of the mammillary nucleus are two fascicles of nerve

fibers. The more caudal one is the mammillotegmental tract, an efferent pathway

from the hypothalamus that terminates in the reticular formation located in the ventral

tegmental area of the midbrain. The more rostral fascicle is the mammillothalamic

tract. The latter will be discussed in more detail in the next laboratory session when the

limbic system is studied.

NEURORADIOLOGY

On slide 45, the hypothalamus can be seen ventral to the hypothalamic

sulcus. The mammillary bodies and infundibulum can also be seen. On slide 50

and slide 65, find the mammillary bodies, hypothalamus and third ventricle.

NOTES














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THE LIMBIC SYSTEM

Objectives: 1. Learn, and be able to identify, the structures that make up the limbic

system, including the “Papez Circuit.”

2. Be able to relate the above anatomy to function.

The limbic system is that part of the brain controlling emotion, motivation,

learning and memory, and sexual behavior. It is composed of a series of cortical and

subcortical structures connected by fiber systems that join these cortical and subcortical

structures together to form "closed loop" circuits. However, many of the structures in

these loops either receive afferents from other areas of the brain and/or project efferent

axons to other structures outside these so called "closed loop" circuits. This enables

the limbic system to influence a wide range of behaviors based on a variety of sensoryinputs.

The original closed loop circuit for the limbic system was described by James

Papez in 1937 and bears his name (Papez Circuit). This closed loop circuit is organized

as follows: hippocampal formation → via fornix → mammillary bodies → via

mammillothalamic tract → anterior nuclear group of the thalamus → via anterior limb of

internal capsule → cingulate cortex → via cingulum → parahippocampal (entorhinal)

cortex → perforant pathway → hippocampal formation.

As our understanding of this complex system has grown, other nuclear structures

and pathways have been added. These include the amygdala, which has direct

connections with the hippocampal formation. In addition, the amygdala has connections

with: 1) wide areas of the hypothalamus and dorsomedial nucleus of the thalamus

(which projects to the frontal lobe) via the stria terminalis and/or ventral amygdalofugal

pathway; 2) septal nuclei via the diagonal band of Broca and; 3) habenular nuclei via

the stria terminalis and stria medullaris. (NOTE: indirect connections to the habenular

nuclei are relayed through the septal nuclei and hypothalamus).

The primary purpose of the above discussion is not necessarily for the

ANATOMY per se, but to allow the student to appreciate the numerous and complexinterconnections between limbic structures as well as the broad interconnections

between the limbic system and the rest of the brain. As one might surmise, these

interconnections are critical to the functional integrity of this complex system.

The cortical components of the limbic system will be identified first, followed by

subcortical components and finally the pathways that connect these components.



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Half brain; Coronal and Horizontal Sections

Cortical components -- Turn your half brain specimens to observe the medial surface.

Immediately rostral to the anterior commissure and lamina terminalis is a small vertical

strip of cortex called the paraterminal gyrus. Just rostral to the paraterminal gyrus and

immediately ventral to the rostrum of the corpus callosum is the subcallosal gyrus.

These two gyri together are often referred to as the septal area. Follow the subcallosal

gyrus rostrally to the genu of the corpus callosum where the subcallosal gyrus becomes

the cingulate gyrus. The cingulate gyrus extends along the dorsal surface of the

corpus callosum from the genu to the splenium. Just caudal to the splenium of the

corpus callosum the cingulate gyrus narrows and dives ventrolaterally as the isthmus

of the cingulate gyrus. The latter is continuous with the parahippocampal gyrus onthe ventromedial surface of the temporal lobe. Due to an involution of the temporal

cortex, the hippocampal formation is hidden from view within the depths of the temporal

lobe just caudal to the uncus. This region of cortex is best seen on a coronal section.

Select a coronal section immediately caudal to the uncus. Just lateral (deep) to

the medial surface of the temporal lobe is an undulating region of cortex buried within

the temporal lobe. This is the hippocampal formation. In more caudal coronal

sections of the hippocampal formation, this structure has the appearance of a sea horse

from which it derives its name (G. hippokampos = sea horse). It is covered ventrally by

the parahippocampal gyrus. The region where the medial lip of the parahippocampal

gyrus bends 180o to turn dorsally and laterally is called the subiculum, a component

part of the hippocampal formation. The remaining parts of the hippocampal formation

will first be seen on slides. It will then be easier for you to identify them on your

coronal/horizontal sections. The paraterminal gyrus, subcallosal gyrus, cingulate gyrus,

isthmus of the cingulate gyrus, parahippocampal gyrus and hippocampal formation form

a continuous cortical circle or rim called the limbic lobe.

Subcortical nuclear components -- Select a coronal section that includes the uncus.Deep (lateral) to the uncus within the temporal lobe is the rounded subcortical nuclear

mass of the amygdala. What sensory pathway has direct connections with the

amygdala? Note the close proximity of the amygdala and the hippocampal formation.

The anterior and dorsomedial nuclei of the thalamus are also prominent anatomical



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components of the limbic system. Find coronal sections that contain these thalamic

nuclei.

Turn again to the medial surface of your half brain specimens. Deep (lateral) to

the septal area and immediately rostral to the anterior commissure are the septal

nuclei (these will be seen on slides). As previously mentioned, the hypothalamus is a

central figure in the limbic system. The habenula, which lies just rostral to the pineal

body, is also typically included as part of the limbic system.

Pathways connecting cortical and subcortical components of the limbic system -- On the

medial surface of the half brain, find the stria medullaris as it arches rostrocaudally

across the medial surface of the thalamus to terminate in the habenula. The stria

medullaris carries afferents to the habenula from the amygdala, septal nuclei and

hypothalamus. Now find the body of the fornix as it arches from caudal to rostralalong the ventral border of the septum pellucidum. The fornix is the major efferent

pathway from the hippocampus. As the fornix approaches the rostral pole of the

thalamus, it dives ventrally as the columns of the fornix (see Fig. 8 below).



78

The majority of axons in the columns of the fornix pass posterior to the anterior

commissure and penetrate the hypothalamus where they synapse in the mammillary

bodies. Those fibers of the fornix passing rostral to the anterior commissure

(precommissural fornix) terminate primarily in the septal nuclei and anterior

hypothalamus.

As the fornix arises from the hippocampus, it arches caudally and dorsally toward

the splenium of the corpus callosum. This can be seen in both horizontal and coronal

sections. Select a coronal section immediately caudal to the uncus and a horizontal

section looking down on the dorsal aspect of the thalamus just ventral to the body of the

corpus callosum. On the coronal section, note the thin strip of white matter that forms

the lateral wall of the hippocampal formation. This is the alveus and is formed by the

efferent fibers arising from the hippocampus. The alveus courses dorsomedially to form

a free lip of white matter called the fimbria, the initial portion of the fornix. Select amore caudal coronal section through the splenium of the corpus callosum (if possible)

and observe the fimbriae as they arch dorsomedially to form the crura (sing. = crus) of

the fornix. As the crura approach the midline to form the body of the fornix, you may

be able to see a membranous sheet of tissue fusing the left and right fornix. This is the

commissure of the fornix (hippocampal commissure).

At this time, try to find the crura, hippocampal commissure and the body and

columns of the fornix on the horizontal sections. NOTE: If you cannot find the above

structures on your sections due to the "luck of the cut", look on your neighbor's

specimens and/or look at the demonstrations.

Now find a horizontal section just ventral to the body of the corpus callosum and

look at the dorsal aspect of the intact thalamus (if your "luck of the cut" allows this view).

The rounded mass along the dorsolateral aspect of the thalamus is the caudate

nucleus. In the rostrocaudal groove between these two structures is a thin bead of

white matter called the stria terminalis. It may be hidden from view by the

thalamostriate (terminal) vein or choroid plexus. If so, look on your neighbor’s brain or

the demonstrations. What are the origin and termination of axons in the stria

terminalis? Now follow the body of the fornix, stria terminalis and stria medullaris

rostrally on your coronal sections. Note the relationship between the columns of the

fornix and the anterior commissure. In a section containing the anterior thalamic nuclei

and/or the mammillary bodies, you may be able to find the columns of the fornix as

they dive ventrally within the substance of the hypothalamus to terminate in the



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mammillary bodies. In the same section(s), try to find the mammillothalamic tract,

which loops dorsally from the mammillary bodies to terminate in the anterior nucleus of

the thalamus. To what cortical region does the anterior nucleus of the thalamus

project? Find the cingulate gyrus on your coronal sections. The white matter

immediately deep to the gray matter of the cingulate cortex is the cingulum, which

contains the efferent axons from the cingulate gyrus to the parahippocampal gyrus.

Slide Set

The following slides (26-36,38,39) will reveal cortical regions and subcortical nuclei as

well as pathways of the limbic system. As you proceed through these slides, attempt to

correlate them with the wet brain specimens.

Begin with slide 26. Immediately dorsal to the pulvinar on both sides lie thecrura of the fornix. Sandwiched between the crura is the caudal extent of the body of

the corpus callosum. Just lateral to the fornix lies the body of the caudate nucleus.

The relatively small brown-stained region just ventral to the caudate nucleus is the stria

terminalis. The lower left side of this slide reveals a coronal section through the

temporal lobe at the level of the hippocampal formation, which is composed of the

hippocampus proper, dentate gyrus and subiculum. The cortical region medially and

ventrally is the parahippocampal gyrus. The region of this gyrus dorsally where it

swerves laterally is called the subiculum. Where the subiculum meets the overlying

dentate gyrus, it becomes the hippocampus proper. The groove between the

hippocampus proper and the overlying dentate gyrus is called the hippocampal

fissure. The darkly stained white matter dorsal to the dentate gyrus is the fimbria of

the fornix, which tapers laterally as the alveus.

A higher power view of the hippocampus proper can be seen on slide 27. On

this slide, identify the subiculum, dentate gyrus, hippocampal fissure,

hippocampus proper, alveus and fimbria of the fornix. Note that the hippocampus

proper extends laterally from the hippocampal fissure and arches dorsally to terminate

by tucking its "head" into the dentate gyrus. Identify the choroid plexus stretchingbetween the fimbria of the fornix and the region just medial to the stria terminalis which

is embedded in the roof of the inferior (temporal) horn of the lateral ventricle. The

nuclear mass in the roof of the lateral ventricle lateral to the stria terminalis is the tail of

the caudate nucleus, part of the basal ganglia. The space medial to the choroid plexus










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is the subarachnoid space, whereas the space lateral to the choroid plexus is the

inferior (temporal) horn of the lateral ventricle.

Slide 28 is slightly more rostral and contains the habenular nuclei. Find the

crura and fimbria of the fornix, and the alveus. The stria terminalis can also be

seen between the thalamus and body of the caudate nucleus as well as in the roof of

the inferior horn of the lateral ventricle. Slide 29 also contains the habenular nuclei

in addition to the habenulointerpeduncular tract (fasciculus retroflexus). This output

pathway from the limbic system arches ventrally and caudally to synapse in the RF of

the midbrain tegmentum. Also note the appearance of the mammillary bodies on this

slide.

Slide 30 illustrates the origin of the mammillothalamic tract as it arises from the

medial aspect of the mammillary nuclei. Where does this fiber tract terminate? Within

the lateral aspect of the mammillary nuclei are pale blue vertical strips. These are theterminal fibers of the columns of the fornix. Also note the lightly stained uncus of the

temporal lobes located ventrolateral to the mammillary bodies. The region deep

(lateral) to the uncus is the amygdala.

Slide 31 shows the body and columns of the fornix, stria terminalis, stria

medullaris, mammillothalamic tract, uncus and amygdala. Nerve fibers from the

amygdala can be seen arching dorsomedially as the ventral amygdalofugal pathway

(see the labeled illustration of slide 31 in the atlas at the back of this syllabus), which

terminates primarily in the dorsomedial nucleus of the thalamus. Also note the

compact bundle of nerve fibers in the temporal lobe. These are the fibers of the

anterior commissure as they proceed rostrally before they cross the midline. As such,

follow the fiber bundles of the anterior commissure rostrally on subsequent slides until

they meet at the midline.

Slide 32 and slide 33 illustrate the body and columns of the fornix, stria

medullaris and mammillothalamic tract. The latter can be seen as a tangentially cut

fascicle of axons dorsolateral to the hypothalamic sulcus on slide 32. On slide 33, it is

visible on the right side as a looping fascicle of axons approaching the anterior nuclear

group from the ventral side. Slide 33 also shows the mammillotegmental tract as athin tract of axons just medial and dorsal to the columns of the fornix. This pathway

descends to the RF in the midbrain tegmentum.

Slide 34 shows the columns of the fornix in two different planes. Just ventral to

the body of the corpus callosum, the fibers of the columns of the fornix are cut in



































81

longitudinal section. In contrast, they are cut in cross section as they pass caudal to the

anterior commissure.

Slide 35 and slide 36 are horizontal sections through the thalamus. The septal

nuclei can be seen just rostral to the columns of the fornix in slide 36.

Slide 38 is a cellular stain of a coronal section through the anterior

commissure. Find the columns of the fornix and the septal nuclei.

On slide 39, find the body and columns of the fornix, anterior commissure,

mammillary body, mammillotegmental tract, mammillothalamic tract, anterior

nucleus of the thalamus and dorsomedial nucleus of the thalamus.

NEURORADIOLOGY

On slide 45, find the paraterminal gyrus, cingulate gyrus, isthmus of thecingulate gyrus and the fornix. What region on this slide represents the septal area?

Slide 46 shows the hippocampal formation. Slide 47 shows the crura of the fornix,

while slide 48 and slide 49 illustrate the columns of the fornix.

DEMONSTRATIONS

Whole brain (ventral view) showing: Hippocampal Formation, fornix.

Whole brain (dorsal view) showing: Hippocampal Commissure, StriaTerminalis, Stria Medullaris.

NOTES





































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VISUAL SYSTEM

Objectives: 1. Know the functional anatomy of the globe of the eye.

2. Know the anatomy & function of the primary visual pathway and the

consequences of a lesion to any part of this pathway.

The visual system is a delicately balanced, highly complex system that enables

us to see our environment in great detail, and in color. The act of "seeing" or visualizing

an object occurs in two phases: The first phase involves light reflecting from an object

and passing into the globe of the eye via the cornea. Within the eye, the lens directs

and focuses the light onto a specialized region at the back of the eye called the retina.

The second stage of visualization is the conversion of this light energy into electrical

impulses by the retina. Ganglion cells within the retina give rise to axons that form theoptic nerve. Visual information that has been processed by the retina is transmitted

through the optic nerve to the optic chiasm where some axons enter the hypothalamus

to influence diurnal rhythms. The majority of nerve fibers enter the optic tracts, which

project axons to the primary visual cortex in the occipital lobe via a relay in the lateral

geniculate body of the thalamus. The primary visual cortex then relays this visual

information to other areas of the cerebral cortex for further processing and analysis.

Some of the optic tract fibers bypass the lateral geniculate to project into the rostral

midbrain where they provide the input for visual reflexes (pupillary dilation and

constriction, accommodation and eye movements in response to visual stimuli).

Globe of the eye (slides 41-44) -- We will begin our study of the visual system by

examining the globe of the eye. Slide 44 shows a low power view of a horizontal

section cut through the equator of the eye. Find the cornea, anterior chamber, iris,

lens, posterior chamber, ciliary body and ciliary processes. Now turn to slide 41

and identify these same structures on this higher power view. Also observe the

pigmented layer of the iris on this slide. What effect does contraction of the muscles

of the ciliary body have on the tension applied to the lens? What effect does this have on the shape of the lens? Would a lesion of the superior cervical sympathetic ganglia

have any effect on the shape of the lens? Why (or why not)? Now turn back to slide 44

and identify the vitreous chamber, retina, optic disc, central artery to the retina,

optic nerve and dura mater, arachnoid mater and subarachnoid space. Can you

explain why the optic nerve is surrounded by meninges? Slide 43 is a high power view

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83

of the macula lutea, the region of the retina that produces the best visual acuity, and

the posterior wall of the eye. Note the three visible cell layers of the retina, the visual

receptor cells (rods and cones), bipolar cells and ganglion cells. The depressed

area at the center of the macula lutea is the fovea centralis. What is the unique

feature of this region? Also identify the pigment layer of the retina, the choroid layer

and the sclera. Between what layers does retinal detachment occur? Why is it

important to reattach the retina as soon as possible? Now observe slide 42. This is a

high power view of the optic disk and optic nerve. Why is the optic disk called the

"blind spot"? Where are the cell bodies of origin for the nerve fibers in the optic nerve?

Nerve fibers arising from the nasal (medial) half of the retina cross to the contralateral

side of the brain via the optic chiasm. The remaining nerve fibers from the temporal

(lateral) half of the retina remain ipsilateral.

The remainder of the visual pathway can be seen on slides 23-26,28,29,31-33and on demonstration. To better understand the plane of section on each of these

slides, compare each slide with your half brain specimen. For example, look at slide

33. At the bottom of the slide in the midline is a small part of the infundibulum. Find

this structure on your half brain just posterior to the optic chiasm. Approximately in the

middle of the slide is the massa intermedia. Find this structure on your half brain.

Now draw an imaginary line between the infundibulum and the massa intermedia. This

is the plane of section on slide 33. Note the optic tract (slide 33 and slide 32) just

lateral to the hypothalamus. Follow the optic tract posteriorly as it diverges to lie just

ventral to the cerebral peduncles (slide 31, slide 30 and slide 29). On the left side of

slide 28, the terminal portion of the optic tract can be seen entering the laminated

lateral geniculate. On slide 28, slide 26 and slide 23, the optic radiations can be

seen emerging from the dorsolateral aspect of the lateral geniculate bodies as they

head for the primary visual cortex (area 17). Slide 25 reveals the optic chiasm, optic

tract and lateral geniculate. The fibers of the brachium of the superior colliculus

can be seen after they exit the optic tract to wind around the dorsal aspect of the medial

geniculate just ventral to the pulvinar to enter the pretectal area. Some of these fibers

cross the midline in the posterior commissure. What is the function of this pathway? What is the plane of section in slide 25 ? The brachium of the superior colliculus,

optic tract, medial geniculate, lateral geniculate and pulvinar can also be clearly

seen on slide 23.

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84

Coronal and Horizontal Sections; Half Brain

Coronal sections -- Starting with the section through the optic chiasm, follow the

optic tracts caudally to the lateral geniculate bodies and note the optic radiations

emerging from the lateral geniculate bodies. At the level of the medial and lateralgeniculate bodies, attempt to find the brachium of the superior colliculus.

Horizontal sections -- Select the section that contains the anterior commissure

and if possible, find the medial and lateral geniculate bodies. This section should

also reveal the optic radiations. It should be noted at this time that axons within the

optic radiations that serve the upper visual fields (lower retinal fields) travel rostrally

from the lateral geniculates to loop around the rostral pole of the temporal horn of the

lateral ventricles before they turn caudally to join the remaining optic radiations and

terminate in the primary visual cortex. Consequently, lesions of the temporal lobe may

result in visual field deficits. This indirect pathway is called Meyer’s loop (see

demonstration). On the section immediately ventral to this one, try to find the optic

tracts as they wind around the brainstem just anterior (ventral) to the cerebral

peduncles. NOTE: Whether you see some of these structures will rely on the "luck of

the cut". If you are unable to see the above structures on your sectioned brains, look on

the brain specimens of one of your neighbors.

Half brain -- On the medial surface, find the parietooccipital sulcus and thecalcarine sulcus. The cortex surrounding the dorsal and ventral lips of the calcarine

sulcus is the primary visual cortex (area 17), which receives afferents from the

ipsilateral lateral geniculate bodies. A good portion of the primary visual cortex is

hidden from view, since the calcarine sulcus extends laterally into the occipital cortex.

The general cortical region dorsal to the calcarine sulcus is the cuneus. Its counterpart

ventral to the calcarine sulcus is the lingula.

NEURORADIOLOGY

Find the optic nerve, optic chiasm, calcarine fissure, cuneus and lingula on

slide 45. Can you find the lateral geniculate bodies on slide 46 ? (Hint: Compare

this slide with your coronal brain specimens). The optic radiations can be clearly seen

on slide 47, slide 48 and slide 49. A lesion of the optic radiations on the right side



















85

would cause what clinical symptom(s)? Could a lesion of the temporal lobes cause

visual field deficits? On slide 64, find the optic nerves and globes of the eyes. On

slide 65, find the optic tracts.

DEMONSTRATIONS

Visual pathway – optic nerve, optic chiasm, optic tract, lateral geniculate,

brachium of superior colliculus, superior colliculus, optic radiations.

Globe of the eye (cow’s eye) – vitreous chamber, sclera, choroid layer, retina,

optic disk, central retinal vessels, ora serrata, lens, ciliary processes, cornea, ant.

chamber, iris, post. chamber. Use Fig. 7 below to assist you in identifying the

structures of the cow’s eye.









86

NOTES



87

CEREBRAL CORTEX AND REVIEW

Objectives: 1. Revisit those areas of primary cortex previously learned and review

their location and function.

2. Learn & understand other areas of cortex presented here with

particular emphasis on those areas related to speech.

3. Know the clinical symptoms related to lesions of cortical areas as

presented in lecture.

The cerebral cortex is composed of: 1) a convoluted sheet of neurons at the

external surface of the cortex and 2) the subjacent white matter that interconnects the

cells of the cerebral cortex with other cortical cells and with cells in other regions of the

CNS. It is the well-developed cerebral cortex in humans that gives us our uniqueabilities to participate in language and abstract thinking. The cerebral cortex is also

critically involved in our perception of the outside world and our ability to move and

adapt to our environment.

The vast majority of the cerebral cortex (over 90%) is classified as neocortex. As

the name implies, it is the most recent type of cortex to develop. The classification of

the types of cerebral cortex is largely based on the histological cytoarchitecture of the

outer mantle of cortical cells as follows:

1. Neocortex (Isocortex) -- classically described as those regions of

cerebral cortex that contain, either during development or in the adult

stage, 6 layers of cells from superficial to deep.

2. Paleocortex -- contains from 3 - 5 layers of cells, and is restricted to

the primary olfactory cortex on the ventral surface of the brain.

3. Archicortex -- contains 3 layers of cells, and is restricted to the

hippocampal formation.

Through the years, a number of anatomists have attempted to categorize the

cerebral cortex based on neural cytoarchitecture. It was originally thought that the

anatomical differences between different areas of the cortex could be precisely related

to function. Although none of the published classifications have achieved the specificity



88

that was originally hoped for, overall, Brodmann's (circa 1909) numerical classifications

of 52 cortical regions have emerged as the standard and have generally withstood the

test of time. However, as more information is gathered on brain function using more

sophisticated research techniques, our understanding of the functioning of the various

regions of the cerebral cortex, and the CNS as a whole, is rapidly evolving.

To ease your fears, we will not attempt to identify all of Brodmann's 52 areas of

the cerebral cortex, but instead concentrate on those areas that relate to a specific

modality or function. It should be noted that much of this laboratory session will be a

review of cortical areas we have already studied. However, this laboratory will also give

you the opportunity to review pathways related to a number of cortical regions. For

example, Brodmann's area 4 of the precentral gyrus contributes axons to the

corticospinal and corticobulbar pathways. You should be able to identify the location of

these pathways on both your wet brain specimens and your slide sets.You should perform this exercise on all known ascending and descending pathways.


On the left lateral surface of the cerebral cortex, identify the central sulcus,

precentral gyrus, and the superior, middle and inferior frontal gyri. Make sure you

understand the somatotopic arrangement of the precentral gyrus. Identify the general

region of the premotor area (area 6) and frontal eye fields (area 8). An ablative

lesion of area 8 on the left side results in what symptom(s)? Find the Sylvian fissure.

The inferior frontal gyrus lies on the superior bank of this fissure just rostral to the

precentral gyrus and is divided into three parts from caudal to rostral. The opercular

part of the inferior frontal gyrus is small and lies just rostral to the precentral gyrus;

the triangular part resembles an inverted triangle. Both the opercular and triangular

portion represent Broca's speech area (areas 44,45). Lesion of this area results in

Broca's aphasia. What are the symptoms of Broca's aphasia? What region of the body

is controlled by the precentral gyrus immediately caudal to Broca's area? The

horizontal gyrus just rostral to the triangular portion of the inferior frontal gyrus is theorbital part of the inferior frontal gyrus. If the Sylvian fissure is gently opened, the

insular cortex can be seen. Can you name two sensory modalities that terminate in

the insular cortex?

On a lateral view of the left temporal lobe, find the superior, middle and inferior

temporal gyri. The dorsal surface of the superior temporal gyrus is hidden by the



89

frontal and parietal opercula, and contains the transverse gyri of Heschl (areas

41,42). What symptom(s) would you expect to observe if Heschl's gyri were lesioned on

the left side? The lateral surface of the superior temporal gyrus, approximately from the

level of the precentral gyrus rostrally to the posterior portion of the supramarginal

gyrus caudally, contains the auditory association area (area 22). The posterior

portion of area 22 is Wernicke's area, which acts to integrate visual and auditory

information required to comprehend written and spoken language. A lesion of this area

results in Wernicke's aphasia. Can you describe the symptoms of Wernicke's

aphasia?

Immediately caudal to the supramarginal gyrus of the parietal lobe is the

angular gyrus. These two gyri form the inferior parietal lobule. A lesion of the

inferior parietal lobule, but not Wernicke's area, results in a complex series of disorders

which may include any combination of the following: alexia, anomia, constructionalapraxia, agraphia, finger agnosia and confusion or inability to distinguish between the

left and right sides of the body. Can you define the above terms that describe this

lesion? What symptoms would you expect to see in a comparable lesion of the right

cerebral hemisphere? What artery supplies this region? Find the postcentral gyrus

(areas 3,1,2). This is the somatosensory cortex. What pathways terminate along this

somatotopically arranged gyrus?

Find the calcarine fissure at the caudal pole of the occipital lobe. The gyri

forming the upper and lower lips of this fissure are the primary visual cortex (area 17).

The visual association areas (areas 18 and 19), are arranged concentrically around

area 17 on the lateral surface of the occipital lobe. Now follow the calcarine fissure

around to the medial surface of the occipital lobe, where this fissure forms a deep

horizontal groove that projects laterally. Thus, although area 17 can be seen

immediately dorsal (cuneus) and ventral (lingula) to the calcarine fissure, much of area

17 is hidden from view within the depths of the occipital lobe. As on the lateral surface

of the occipital lobe, areas 18 and 19 surround area 17. What symptoms would result

following a lesion of the left primary visual cortex? What major artery supplies this

region? Follow the calcarine fissure rostrally where it is joined by the parietooccipitalsulcus. Find the cingulate gyrus, the isthmus of the cingulate gyrus and the

paracentral lobule. What Brodmann's areas are encompassed by the paracentral

lobule? What part(s) of the body does the paracentral lobule serve? Is the paracentral

lobule sensory or motor? What symptoms would you see if it were lesioned? What

artery supplies the paracentral lobule? Follow the cingulate gyrus as it curves ventrally



90

around the genu of the corpus callosum to become the subcallosal gyrus. Also

identify the paraterminal gyrus. What diencephalic nucleus projects to the cingulate

gyrus? To what important system does the cingulate gyrus belong?

Turn to the ventral surface of the brain and identify the uncus and

parahippocampal gyrus. What important structure lies deep to the uncus? What

clinical symptoms would you see if this structure was lesioned bilaterally? What is the

classification of cerebral cortex that comprises the uncus?

The remaining areas of cortex come under the broad heading of association

cortices, which correlate the various sensory inputs and deliver them to the appropriate

cortical areas for action.

Intercortical Connections -- Afferent input to the cerebral cortex comes from a variety

of subcortical structures. As you have probably surmised by now, it is the thalamus, viathe internal capsule, that provides the greatest single source of subcortical input to the

cerebral cortex. Similarly, efferents from the cerebral cortex also pass to subcortical

structures primarily through the internal capsule.

With the possible exception of the visual cortex, virtually all areas of the cerebral

cortex interconnect across the midline with comparable cortical areas via subcortical

white matter called commissural fibers (pathways). Ipsilateral connections (within the

same hemisphere) are accomplished by way of association fibers.

Commissural fibers -- Turn to the medial surface of your half brain sections.

Identify the rostrum, genu, body and splenium of the corpus callosum. It is this

massive interhemispheric commissure that provides the vast majority of commissural

fibers between the cerebral hemispheres. The anterior commissure also transmits

interhemispheric fibers between the temporal lobes. Why isn't the posterior commissure

included in this group of commissural fibers?

Association fibers -- The association fiber bundles are difficult to see. However,

their general location can be determined. Select a coronal section midway through thebody of the corpus callosum and identify the location of the following fiber bundles

within the white matter deep to the cellular layers of the cerebral cortex. The white

matter immediately deep (lateral) to the cingulate cortex is the cingulum, which

connects the cingulate cortex with the parahippocampal gyrus and hippocampal

formation. The region of white matter immediately dorsal to the body of the caudate



91

nucleus at the lateral extent of the lateral ventricle contains the superior

occipitofrontal fasciculus (subcallosal bundle) which interconnects the more dorsal

(superior) portions of the occipital, parietal and frontal lobes. Just dorsal to the insular

cortex lies the superior longitudinal (arcuate) fasciculus, which interconnects

ipsilateral frontal, parietal, occipital and temporal lobes. It is the arcuate fasciculus that

interconnects Wernicke's and Broca's areas. A lesion of the arcuate fasciculus deep to

the parietal operculum produces conduction aphasia. What are the symptoms of

conduction aphasia? The inferior occipitofrontal fasciculus is located in the white

matter of the temporal lobe ventral to the insular cortex. This fiber bundle interconnects

ipsilateral frontal, temporal and occipital lobes. Some of the more ventral fibers of this

fasciciulus interconnect the orbital cortex of the frontal lobe and the anterior temporal

cortex by hooking around the deep margins of the Sylvian fissure to sweep rostrally into

the temporal lobe as the uncinate fasciculus (will not be seen).

Cerebral Dominance -- In our study of the cerebral hemispheres thus far, they have

appeared separate, but equal. That is, there have been similar functions in similar

locations in both hemispheres, and each hemisphere primarily controls functions of the

contralateral side of the body. However, this concept cannot be applied to the important

function of language, which typically resides in one hemisphere only. That hemisphere

that controls language is generally agreed to be the dominant hemisphere. In over 90%

of humans, the dominant hemisphere is the left hemisphere. The dominant hemisphere

is also related to handedness, since 95% of right-handed individuals are left hemisphere

dominant. This number drops to approximately 50% in left-handed individuals. It

should be noted that a few individuals possess language areas in both hemispheres. It

should also be remembered that the non-dominant (usually right) hemisphere should

not be viewed as less important, since it is the "dominant" hemisphere when it comes to

artistic talent, music and spatial perception.

DEMONSTRATIONS

Insula, Broca's area, Wernicke's area, Heschl's gyri.

Brodmann's areas.



92

NOTES



93

Labeled Atlas of Representative Sections ofSpinal Cord and Brain from your Slide Set



SLIDE 1

SACRAL SPINAL CORD

1. Fasciculus gracilis2. Lateral corticospinal tract3. Lateral spinothalamic tract4. Ventral (anterior) spinothalamic tract

5. Nucleus proprius6. Substantia gelatinosa7. Lissaur’s tract 8. Ventral (anterior) white commissure9. Ventral motor horn cells10. Ventral median fissure

* Cauda equina (v=ventral & d=dorsal roots)

Fix Atlas: plate 12

1

3

4

5

6

7

2

8

9

10

*

*

*

*

*

v v

d

dd



SLIDE 5

UPPER CERVICAL SPINAL CORD (C-1)

1. Fasciculus gracilis2. Fasciculus cuneatus3. Lateral spinothalamic tract4. Spinotectal tract5. Ventral (anterior) spinothalamic tract

6. Spinal nucleus of V7. Spinal tract of V8. Lateral corticospinal tract9. Spinal accessory nucleus10. Lateral vestibulospinal tract11. Medial vestibulospinal tract

(medial longitudinal fasiculus)12. Ventral (anterior) corticospinal tract

13. Ventral (anterior) white commissure14. Ventral median fissure

1

2

7

6

3

5

8

9

12

13

14

Fix Atlas: plate 19

1110

4



SLIDE 7

MEDULLA – MOTOR DECUSSATION

1

3

5

1. Fasciculus cuneatus2. Spinal tract of V3. Spinal nucleus of V4. Spinal lemniscus (lateral & ventral spinothalamic tracts and spinotectal tra5. Nucleus gracilis

6. Nucleus cuneatus7. Internal arcuate fibers8. Motor (pyramidal) decussation9. Pyramids

2

4

67

8

9 9

Fix Atlas: plate 21



SLIDE 8

MEDULLA – SENSORY DECUSSATION

1

2

3

4

6

5 5

8

9

1

1112

13

1. Nucleus cuneatus2. Spinal tract of V3. Spinal nucleus of V4. Spinal lemniscus5. Medial lemniscus

6. Internal arcuate fibers7. Medial longitudinal fasciculus (MLF)8. Fasciculus cuneatus9. Nucleus gracilis10. Tractus solitarius (surrounded by nuc. solitarius)11. Dorsal motor nucleus of X12. Hypoglossal nucleus13. Pyramid

7

Fix Atlas: plate 22



SLIDE 9

ROSTRAL MEDULLA

Fix Atlas: plates 23/2

1

23

4

5

6

7

89

1011

12

13

1. Hypoglossal nucleus2. Dorsal motor nucleus of X3. Tractus solitarius (surrounded by nuc. solitarius)4. Spinal tract of V

5. Spinal nucleus of V6. Spinal lemniscus7. Inferior olivary nucleus8. Hypoglossal n. (CN XII) in preolivary sulcus9. Pyramid10. Nucleus cuneatus11. Inferior cerebellar peduncle (restiform body)12. Medial longitudinal fasciculus (MLF)

13. Medial lemniscus



SLIDE 12

ROSTRAL MEDULLA - 2

Fix Atlas: plate 25

1. Nucleus prepositus2. Medial vestibular nucleus3. Tractus solitarius (surrounded by nuc. solitarius)4. Foramen of Luschka (containing choroid plexus)5. Ventral cochlear nucleus6. Olivocerebellar pathway7. Spinal lemniscus

8. Pyramid9. Dorsal cochlear nucleus10. Inferior (spinal) vestibular nucleus11. Inferior cerebellar peduncle12. Medial longitudinal fasciculus (MLF)13. Spinal tract of V14. Spinal nucleus of V15. Nucleus ambiguus

16. Vagus n. (CN X) in postolivary sulcus17. Medial lemniscus

123

4

5

6

7

8

910

1112

1314

15

16

17



SLIDE 15

MEDULLARY – PONTINE JUNCTION

Fix Atlas: plates 26/2

1. Medial longitudinal fasciculus (MLF)2. Juxtarestiform body3. Spinal tract of V4. Spinal nucleus of V5. Spinal lemniscus6. Central tegmental tract7. Facial n. (CN VII)8. Middle cerebellar peduncle (brachium pontis)9. Ventral pons

10. Inferior (spinal) vestibular nucleus11. Medial vestibular nucleus12. Inferior salivatory nucleus13. Tractus solitarius (surrounded by nuc. solitarius)14. Inferior cerebellar peduncle15. Ventral cochlear nucleus16. Vestibulocochlear n. (CN VII)17. Nucleus ambiguus18. Olivocerebellar pathway

19. Inferior olivary nucleus20. Pyramid21. Medial lemniscus

1

2

43

5

7

6

8

9

1110

12

1314

15

16

17

18

192021



SLIDE 16

CAUDAL PONS

Fix Atlas: plate 29

1. Facial colliculus2. Internal genu of CN VII3. Medial longitudinal fasciculus (MLF)4. Abducens nucleus5. Medial vestibular nucleus6. Lateral vestibular nucleus7. Superior vestibular nucleus8. Superior cerebellar peduncle

9. Inferior cerebellar peduncle10. Middle cerebellar peduncle11. Juxtarestiform body12. Fascicles of CN VI13. Fascicles of CN VII (in pontine tegmentum)14. Superior olivary nucleus15. Lateral lemniscus16. Spinal lemniscus17. Medial lemniscus

18. Pontine nuclei19. Spinal tract of V20. Spinal nucleus of V

21. Facial nucleus22. Vestibulocochlear n. (CN VIII)23. Facial n. (CN VII)24. Central tegmental tract25. Abducens n. (CN VI)26. Corticospinal & corticobulbar tracts

27. Trapezoid body

12 3 4

56

78

9

101112

13

141516

17

18 242326

25

27



SLIDE 18

MID-PONS

Fix Atlas: plate 30

1. Medial longitudinal fasciculus (MLF)2. Motor root of CN V3. Trigeminal lemniscus4. Lateral lemniscus5. Spinal lemniscus6. Medial lemniscus7. Pontine nuclei8. Corticospinal & corticobulbar tracts9. Superior vestibular nucleus10. Mesencephalic tract (root) of V

surrounded by mesencephalic nucleus of V11. Chief (principal) sensory nucleus of V12. Motor nucleus of V13. Middle cerebellar peduncle14. Central tegmental tract15. Transverse pontine (pontocerebellar) fibers

1

2

3

4

5

6

7

8

9

1

1

1

13

1

1



SLIDE 20

ROSTRAL PONS

Fix Atlas: plate 33

12

3

54 7

8

6

9

1010

11

12

1. Decussation of CN IV within superior medullary velum2. Medial longitudinal fasciculus (MLF)

3. Trochlear n. (CN IV)4. Lateral lemniscus5. Spinal lemniscus6. Medial lemniscus7. Trigeminal lemniscus8. Descending portion of CN IV9. Nucleus of lateral lemniscus10. Superior cerebellar peduncle

11. Central tegmental tract12. Decussation of superior cerebellar peduncles



SLIDE 21

CAUDAL MIDBRAIN

Fix Atlas: plate 35

1. Nucleus of the inferior colliculus2. Periaqueductal gray3. Mesencephalic nucleus of V & tract of V (lateral to nucleus of V)4. Medial longitudinal fasciculus (MLF)5. Trochlear nucleus & CN IV arising laterally6. Decussation of superior cerebellar peduncles7. Substantia nigra8. Corticospinal tract9. Corticobulbar tract10. Fibers forming brachium of inferior colliculus11. Lateral lemniscus

12. Spinal lemniscus13. Trigeminal lemniscus14. Medial lemniscus15. Cerebral peduncle16. Central tegmental tract17. Rubrospinal tract18. Interpeduncular fossa

1 1

45

6

3

78

9

1

1

113

1

15

1

2

1817



SLIDE 23

ROSTRAL MIDBRAIN

Fix Atlas: plate 36

1. Commissure of superior colliculus2. Superior colliculus3. Spinal lemniscus4. Trigeminal lemniscus5. Medial lemniscus6. Central tegmental tract7. Medial longitudinal fasciculus (MLF)8. Oculomotor nuclear complex (& Edinger-Westphal nucleus)

9. Oculomotor n. (CN III)10. Pulvinar of thalamus11. Brachium of the inferior colliculus12. Brachium of the superior colliculus13. Medial geniculate body14. Lateral geniculate body15. Optic tract16. Cerebral peduncle17. Substantia nigra

18. Red nucleus19. Interpeduncular fossa

1

2 2

3

4

5

6

78

9

10

11

12

13

14

15

18

1617

19



SLIDE 27

HIPPOCAMPAL FORMATION

Fix Atlas: plate 50

1

2

3

4 5

6

7

7

7

8

9

9

9

10

1112

13

14 14

1. Tail of the caudate nucleus2. Stria terminalis3. Choroid plexus4. Inferior (temporal) horn of lateral ventricle5. Fimbria of the fornix

6. Alveus7. Hippocampus proper8. Dentate gyrus9. Optic (visual) radiations10. Lateral geniculate body11. Optic tract12. Subarachnoid space13. Hippocampal fissure14. Subiculum



SLIDE 28

THALAMUS / MIDBRAIN / PONS

Fix Atlas: plate 50

1. Body of the corpus callosum2. Crus of the fornix3. Body of the caudate nucleus4. Stria terminalis5. Third ventricle6. Habenula7. Posterior commissure

8. Cerebral aqueduct9. Red nucleus10. Medial lemniscus (& cerebello-rubro-thalamic fibers)11. Medial geniculate body12. Lateral geniculate body13. Fimbria of the fornix14. Hippocampal formation15. Posterior limb of the internal capsule16. Dorsomedial nucleus of the thalamus17. Centromedian nucleus of the thalamus

18. Ventral posterolateral (VPL) nucleus of the thalamus19. Ventral posteromedial (VPM) nucleus of the thalamus20. Cerebral peduncle

21. Optic tract22. Ventral pons

16

13

4

6

2

5

8

7

10

1112

13

14

9

15

1718

19

20

21

22



SLIDE 31

MID-THALAMUS / MAMMILLARY BODIES / AMYGDALA

Fix Atlas: plate 48

1. Body of the corpus callosum2. Body of the fornix3. Body of the caudate nucleus4. Stria terminalis5. Insula6. External capsule7. Putamen8. Globus pallidus

9. Posterior limb of the internal capsule10. Cerebral peduncle11. Ventral amygdalofugal pathway12. Anterior commissure13. Amygdala14. Thalamic fasciculus15. Lateral ventricle16. Third ventricle17. Ventrolateral (VL) nucleus of the thalamus

18. Dorsomedial (DM) nucleus of the thalamus19. Lenticular fasciculus20. Subthalamic nucleus

21. Substantia nigra22. Optic tract23. Fornix24. Mammillary bodies25. Mammillothalamic tract

13

4 2 2

9

9

9

5

6

7

8

10

1112 14

13

15

16

17

18

19

2021

22

132324

25



SLIDE 35

HORIZONTAL THALAMUS

Fix Atlas: plate 56

1. Head of the caudate nucleus2. Putamen3. Interventricular foramen of Monro4. Columns of the fornix5. Dorsomedial (DM) nucleus of the thalamus6. Lateral region of the thalamus7. Body of the fornix

8. Anterior limb of the internal capsule9. Septal nuclei10. Globus pallidus11. Genu of the internal capsule12. Anterior nuclear group of the thalamus13. Posterior limb of the internal capsule14. Stria terminalis15. Tail of the caudate nucleus

* = fusion of the putamen and head of the caudate nucleus

1

*2

3

4

1

56

7

8

11

13

9

12

10

1415



SLIDE 38

HYPOTHALAMUS – Cell Stain

1. Lateral ventricle

2. Septal nuclei3. Columns of the fornix4. Anterior commissure5. Third ventricle

6. Paraventricular nucleus of the hypothalamus7. Supraoptic nucleus of the hypothalamus8. Optic chiasm

* What is this structure (be specific)?

1 1

23

23

4

5

6

7

8

* *

Documents

Neuroscience Lab Manual 2012