Ch 14 Lecture Outline

8/8/2019 Ch 14 Lecture Outline

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Copyright 2010 Pearson Education, Inc.

Functional Brain Systems

Networks of neurons that work together andspan wide areas of the brain

Limbic system

Reticular formation


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Limbic System

Structures on the medial aspects of cerebralhemispheres and diencephalon

Includes parts of the diencephalon and some

cerebral structures that encircle the brainstem


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Copyright 2010 Pearson Education, Inc. Figure 12.18

Corpus callosum

Septum pellucidum

Olfactory bulb

Diencephalic structuresof the limbic system

Anterior thalamicnuclei (flanking3rd ventricle)

HypothalamusMammillary

body

Fiber tractsconnecting limbicsystem structures

FornixAnterior commissure

Cerebral struc-

tures of thelimbic system

Cingulate gyrusSeptal nucleiAmygdalaHippocampus

Dentate gyrusParahippocampalgyrus


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Limbic System

Emotional or affective brain

Amygdalarecognizes angry or fearful facialexpressions, assesses danger, and elicits the

fear response Cingulate gyrusplays a role in expressing

emotions via gestures, and resolves mentalconflict

Puts emotional responses to odors

Example: skunks smell bad


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Limbic System: Emotion and Cognition

The limbic system interacts with the prefrontallobes, therefore:

We can react emotionally to things we

consciously understand to be happening

We are consciously aware of emotional

richness in our lives

Hippocampus and amygdalaplay a role in

memory


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Reticular Formation

Three broad columns along the length of thebrain stem

Raphe nuclei

Medial (large cell) group of nuclei

Lateral (small cell) group of nuclei

Has far-flung axonal connections withhypothalamus, thalamus, cerebral cortex,

cerebellum, and spinal cord


7/68Copyright 2010 Pearson Education, Inc.

Reticular Formation: RAS and Motor Function

RAS (reticular activating system)

Sends impulses to the cerebral cortex to keep

it conscious and alert

Filters out repetitive and weak stimuli (~99% of

all stimuli!)

Severe injury results in permanent

unconsciousness (coma)



Reticular Formation: RAS and Motor Function

Motor function

Helps control coarse limb movements

Reticular autonomic centers regulate visceral

motor functions

Vasomotor

Cardiac Respiratory centers


9/68Copyright 2010 Pearson Education, Inc. Figure 12.19

Visualimpulses

Reticular formation

Ascending generalsensory tracts(touch, pain, temperature)

Descendingmotor projectionsto spinal cord

Auditoryimpulses

Radiationsto cerebralcortex



Electroencephalogram (EEG)

Records electrical activity that accompaniesbrain function

Measures electrical potential differences

between various cortical areas



Ganglia

Contain neuron cell bodies associated withnerves

Dorsal root ganglia (sensory, somatic)

(Chapter 12)

Autonomic ganglia (motor, visceral)

(Chapter 14)



Autonomic Nervous System (ANS)

The ANS consists of motor neurons that:

Innervate smooth and cardiac muscle and

glands

Make adjustments to ensure optimal support

for body activities

Operate via subconscious control



Autonomic Nervous System (ANS)

Other names

Involuntary nervous system

General visceral motor system



Central nervous system (CNS) Peripheral nervous system (PNS)

Motor (efferent) divisionSensory (afferent)division

Somatic nervoussystem

Autonomic nervoussystem (ANS)

Sympatheticdivision

Parasympatheticdivision

Figure 14.1



Somatic and Autonomic Nervous Systems

The two systems differ in

Effectors

Efferent pathways (and their

neurotransmitters)

Target organ responses to neurotransmitters



Effectors

Somatic nervous system

Skeletal muscles

ANS

Cardiac muscle

Smooth muscle

Glands



Efferent Pathways


A, thick, heavily myelinated somatic motor fiber makes

up each pathway from the CNS to the muscle

ANS pathway is a two-neuron chain1. Preganglionic neuron (in CNS) has a thin, lightly

myelinated preganglionic axon

2. Ganglionic neuron in autonomic ganglion has an

unmyelinated postganglionic axon that extends to the

effector organ



Neurotransmitter Effects


All somatic motor neurons release acetylcholine (ACh)

Effects are always stimulatory

ANS

Preganglionic fibers release ACh

Postganglionic fibers release norepinephrine or ACh at

effectors

Effect is either stimulatory or inhibitory, depending on

type of receptors



Skeletal muscle

Cell bodies in centralnervous system Peripheral nervous system Effect

+

+

Effectororgans

ACh

AChSmooth muscle

(e.g., in gut),

glands, cardiac

muscle

Ganglion

Adrenal medulla Blood vessel

ACh

ACh

ACh

NE

Epinephrine andnorepinephrine

Acetylcholine (ACh) Norepinephrine (NE)

Ganglion

Heavily myelinated axon

Lightly myelinated

preganglionic axon

Lightly myelinatedpreganglionic axons

Neuro-transmitterat effector

Unmyelinated

postganglionic

axon

Unmyelinatedpostganglionic axon

Stimulatory

Stimulatory

or inhibitory,

depending

on neuro-

transmitter

and

receptors

on effector

organs

Single neuron from CNS to effector organs

Two-neuron chain from CNS to effector organs

SOMAT

IC

NERVOUS

SYSTEM

AUTON

OM

IC

NERVOUSSYST

EM

PARASYMPATH

ETIC

SYMPATHE

TIC

Figure 14.2



Divisions of the ANS

1.Sympathetic division

2.Parasympathetic division

Dual innervation Almost all visceral organs are served by both

divisions, but they cause opposite effects



Role of the Parasympathetic Division

Promotes maintenance activities andconserves body energy

Its activity is illustrated in a person who

relaxes, reading, after a meal Blood pressure, heart rate, and respiratory

rates are low

Gastrointestinal tract activity is high Pupils are constricted and lenses are

accommodated for close vision



Role of the Sympathetic Division

Mobilizes the body during activity; is the fight-or-flight system

Promotes adjustments during exercise, or

when threatened

Blood flow is shunted to skeletal muscles and

heart

Bronchioles dilate

Liver releases glucose



DivisionOrigin of

FibersLength of

FibersLocation

of Ganglia

Sympathetic Thoracolumbarregion of the

spinal cord

Shortpreganglionic

and longpostganglionic

Close tospinal cord

Parasympathetic Brain andsacral spinalcord

(craniosacral)

Longpreganglionicand short

postganglionic

In visceraleffectororgans

ANS Anatomy


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Salivaryglands

Eye

Skin*

Heart

Lungs

Liverand gall-bladder

Genitals

Pancreas

Eye

Lungs

Bladder

Liver andgall-bladder

Pancreas

Stomach

Cervical

Sympatheticganglia

Cranial

Lumbar

Thoracic

Genitals

Heart

Salivary

glands

Stomach

Bladder

Adrenalgland

Parasympathetic Sympathetic

Sacral

Brainstem

L1

T1

Figure 14.3


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Cranial Nerve Ganglia(Terminal Ganglia)

Effector Organ(s)

Oculomotor (III) Ciliary Eye

Facial (VII) Pterygopalatine

Submandibular

Salivary, nasal, and

lacrimal glandsGlossopharyngeal(IX)

Otic Parotid salivary glands

CranialOutflow

Vagus (X) Within the walls of target organs

Heart, lungs, and mostvisceral organs

SacralOutflow

S2-S4

Within the walls oftarget organs

Large intestine,urinary bladder,ureters, andreproductive organs

Parasympathetic (Craniosacral) Division

Outflow


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Pterygopalatine

ganglion

Eye

Lacrimal

gland

Nasal

mucosa

Ciliary

ganglion

Pterygopalatine

ganglion

Submandibular

ganglion Submandibular

and sublingualglands

CN III

CN VIICN IXCN X

Otic ganglion

Parotid gland

Heart

Lung

Liver and

gallbladder

Stomach

Pancreas

Urinary

bladder

and ureters

Small

intestine

Largeintestine

S2

Pelvic

splanchnic

nerves

Genitalia

(penis,

clitoris, and vagina)

Rectum

Celiac

plexus

Inferior

hypogastric

plexus

Cardiac and

pulmonary

plexuses

S4

Preganglionic

Postganglionic

Cranial nerve

Figure 14.4


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Sympathetic (Thoracolumbar) Division

Preganglionic neurons are in spinal cordsegments T

1 L

2

Sympathetic neurons produce the lateral

horns of the spinal cord

Preganglionic fibers pass through the white

rami communicantes and enter sympathetic

trunk (paravertebral) ganglia


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Superior

cervical

ganglion

Middle

cervical

ganglion

Inferior

cervical

ganglion

Sympathetic trunk

(chain) ganglia

Pons

L2

T1

White rami

communicantes

Liver and

gallbladder

Stomach

Spleen

Kidney

Adrenal medulla

Small

intestine

Large

intestine

Genitalia (uterus, vagina, andpenis) and urinary bladder

Celiac ganglion

Inferior

mesenteric

ganglion

Lesser splanchnic nerve

Greater splanchnic nerve

Superior

mesenteric

ganglion

Lumbar

splanchnic

nerves

Eye

Lacrimal gland

Nasal mucosa

Blood vessels;

skin (arrector pili

muscles and

sweat glands)Salivary glands

Heart

Lung

Rectum

Cardiac and

pulmonary

plexuses

PreganglionicPostganglionic

Sacral

splanchnic

nerves


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Sympathetic Trunks and Pathways

There are 23 paravertebral ganglia in thesympathetic trunk (chain)

3 cervical

11 thoracic

4 lumbar

4 sacral 1 coccygeal


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Copyright 2010 Pearson Education, Inc. Figure 14.5a

Spinal cord

Dorsal root

Ventral root

Sympathetic

trunk ganglion

Sympathetictrunk

Rib

Ventral ramus

of spinal nerve

Gray ramus

communicansWhite ramus

communicans

Thoracicsplanchnic nerves

(a) Location of the sympathetic trunk


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Sympathetic Trunks and Pathways

Upon entering a sympathetic trunk ganglion apreganglionic fiber may do one of the

following:

1.Synapse with a ganglionic neuron within thesame ganglion

2.Ascend or descend the sympathetic trunk to

synapse in another trunk ganglion3.Pass through the trunk ganglion and emerge

without synapsing


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Copyright 2010 Pearson Education, Inc. Figure 14.5b (1 of 3)

To effector

Blood vessels

Skin (arrector

pili musclesand sweat

glands)

Dorsal root ganglionDorsal ramus of

spinal nerve

Dorsal root

Sympathetic

trunk ganglion

Lateral horn (visceral

motor zone)

Ventral root

Sympathetic trunk

Gray ramus

communicansWhite ramus

communicans

Ventral ramus of

spinal nerve

Synapse at the same level

(b) Three pathways of sympathetic innervation

1


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To effector

Blood vessels

Skin (arrector

pili muscles

and sweat

glands)

Synapse at a higher or lower level


2


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Splanchnic nerve

Collateral ganglion

(such as the celiac)

Target organ

in abdomen

(e.g., intestine)

Synapse in a distant collateral ganglion

anterior to the vertebral column


3


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Pathways with Synapses in Chain Ganglia

Postganglionic axons enter the ventral ramivia the gray rami communicantes

These fibers innervate

Sweat glands

Arrector pili muscles

Vascular smooth muscle


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Pathways to the Head

Fibers emerge from T1 T4 and synapse in thesuperior cervical ganglion

These fibers

Innervate skin and blood vessels of the head

Stimulate dilator muscles of the iris

Inhibit nasal and salivary glands


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Pathways to the Thorax

Preganglionic fibers emerge from T1 T6 andsynapse in the cervical trunk ganglia

Postganglionic fibers emerge from the middle

and inferior cervical ganglia and enter nervesC4 C

8

These fibers innervate:

Heart via the cardiac plexus

Thyroid gland and the skin

Lungs and esophagus


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Pathways with Synapses in Collateral

Ganglia

Most fibers from T5 L2 synapse in collateralganglia

They form thoracic, lumbar, and sacral

splanchnic nerves

Their ganglia include the celiac and the

superior and inferior mesenteric


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Pathways to the Abdomen

Preganglionic fibers from T5 L2 travel throughthe thoracic splanchnic nerves

Synapses occur in the celiac and superior

mesenteric ganglia

Postganglionic fibers serve the stomach,

intestines, liver, spleen, and kidneys


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Pathways to the Pelvis

Preganglionic fibers from T10 L2 travel via thelumbar and sacral splanchnic nerves

Synapses occur in the inferior mesenteric and

hypogastric ganglia

Postganglionic fibers serve the distal half of

the large intestine, the urinary bladder, and

the reproductive organs


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Pathways with Synapses in the Adrenal

Medulla

Some preganglionic fibers pass directly to theadrenal medulla without synapsing

Upon stimulation, medullary cells secrete

norepinephrine and epinephrine into the blood


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Visceral Reflexes

Visceral reflex arcs have the samecomponents as somatic reflexes

Main difference: visceral reflex arc has two

neurons in the motor pathway

Visceral pain afferents travel along the same

pathways as somatic pain fibers, contributing

to the phenomenon of referred pain


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Spinal cord

Dorsal root ganglion

Autonomic ganglion

Stimulus

Response

Visceral sensory

neuron

Integration center May be preganglionic

neuron (as shown)

May be a dorsal horninterneuron

May be within wallsof gastrointestinal tract

Sensory receptor

in viscera2

3

1

5 Visceral effector

Efferent pathway(two-neuron chain)

Preganglionic neuron Ganglionic neuron

4


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Referred Pain

Visceral pain afferents travel along the samepathway as somatic pain fibers

Pain stimuli arising in the viscera are

perceived as somatic in origin


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Heart

Lungs and

diaphragmLiver

Stomach

Kidneys

Ovaries

Small intestine

Ureters

Urinarybladder

Colon

Pancreas

Liver

Heart

Appendix

Gallbladder


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Neurotransmitters

Cholinergic fibers release the neurotransmitter ACh All ANS preganglionic axons

All parasympathetic postganglionic axons

Adrenergic fibers release the neurotransmitter NE

Most sympathetic postganglionic axons

Exceptions: sympathetic postganglionic fibers secrete

ACh at sweat glands and some blood vessels inskeletal muscles


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+

AChSmooth muscle

(e.g., in gut),

glands, cardiac

muscle

Ganglion

Adrenal medulla Blood vessel

ACh

ACh

ACh

NE

Epinephrine andnorepinephrine

Acetylcholine (ACh) Norepinephrine (NE)

Ganglion

Lightly myelinated

preganglionic axon

Lightly myelinated

preganglionic axons

Unmyelinated

postganglionic

axon

Unmyelinatedpostganglionic axon

Stimulatory

or inhibitory,depending

on neuro-

transmitter

and

receptors

on effector

organs

Two-neuron chain from CNS to effector organs

AUTONOM

IC

NERVOUSSYST

EM

PA

RASYMPATHETIC

SYMPATHE

TIC


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Receptors for Neurotransmitters

1.Cholinergic receptors for ACh

2.Adrenergic receptors for NE


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Cholinergic Receptors

Two types of receptors bind ACh

1.Nicotinic

2.Muscarinic

Named after drugs that bind to them and

mimic ACh effects


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Nicotinic Receptors

Found on Motor end plates of skeletal muscle cells

(Chapter 9)

All ganglionic neurons (sympathetic andparasympathetic)

Hormone-producing cells of the adrenalmedulla

Effect of ACh at nicotinic receptors is alwaysstimulatory

M i i R


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Muscarinic Receptors

Found on

All effector cells stimulated by postganglionic

cholinergic fibers

The effect of ACh at muscarinic receptors

Can be either inhibitory or excitatory

Depends on the receptor type of the targetorgan


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Copyright 2010 Pearson Education, Inc. Table 14.2

Ad i R t


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Adrenergic Receptors

Two types

Alpha ( ) (subtypes 1, 2)

Beta ( ) (subtypes 1, 2 , 3)

Effects of NE depend on which subclass of

receptor predominates on the target organ


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Eff t f D


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Effects of Drugs

Atropine Anticholinergic; blocks muscarinic receptors

Used to prevent salivation during surgery, and

to dilate the pupils for examination

Neostigmine

Inhibits acetylcholinesterase Used to treat myasthenia gravis

Eff t f D


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Effects of Drugs

Over-the-counter drugs for colds, allergies,and nasal congestion

Stimulate -adrenergic receptors

Beta-blockers

Drugs that attach to 2receptors to dilate lung

bronchioles in asthmatics; other uses


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I t ti f th A t i Di i i


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Interactions of the Autonomic Divisions

Most visceral organs have dual innervation

Dynamic antagonism allows for precise

control of visceral activity

Sympathetic division increases heart and

respiratory rates, and inhibits digestion and

elimination

Parasympathetic division decreases heart andrespiratory rates, and allows for digestion and

the discarding of wastes

S mpathetic Tone


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Sympathetic Tone

Sympathetic division controls blood pressure,even at rest

Sympathetic tone (vasomotor tone)

Keeps the blood vessels in a continual state of

partial constriction

Sympathetic Tone


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Sympathetic Tone

Sympathetic fibers fire more rapidly toconstrict blood vessels and cause blood

pressure to rise

Sympathetic fibers fire less rapidly to promptvessels to dilate to decrease blood pressure

Alpha-blocker drugs interfere with vasomotor

fibers and are used to treat hypertension

Parasympathetic Tone


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Parasympathetic Tone

Parasympathetic division normally dominates theheart and smooth muscle of digestive and urinarytract organs

Slows the heart

Dictates normal activity levels of the digestive andurinary tracts

The sympathetic division can override these effectsduring times of stress

Drugs that block parasympathetic responsesincrease heart rate and block fecal and urinaryretention

Cooperative Effects


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Cooperative Effects

Best seen in control of the external genitalia

Parasympathetic fibers cause vasodilation;

are responsible for erection of the penis or

clitoris

Sympathetic fibers cause ejaculation of

semen in males and reflex contraction of a

females vagina

Unique Roles of the Sympathetic Division


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Unique Roles of the Sympathetic Division

The adrenal medulla, sweat glands, arrector pilimuscles, kidneys, and most blood vessels receiveonly sympathetic fibers

The sympathetic division controls

Thermoregulatory responses to heat

Release of renin from the kidneys

Metabolic effects

Increases metabolic rates of cells

Raises blood glucose levels

Mobilizes fats for use as fuels

Localized Versus Diffuse Effects


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Localized Versus Diffuse Effects

Parasympathetic division: short-lived, highlylocalized control over effectors

Sympathetic division: long-lasting, bodywide

effects

Effects of Sympathetic Activation


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Effects of Sympathetic Activation

Sympathetic activation is long lasting becauseNE

Is inactivated more slowly than ACh

NE and epinephrine are released into theblood and remain there until destroyed by the

liver

Control of ANS Functioning


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Control of ANS Functioning

Hypothalamusmain integrative center ofANS activity

Subconscious cerebral input via limbic lobe

connections influences hypothalamic function

Other controls come from the cerebral cortex,

the reticular formation, and the spinal cord

C i ti t


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Cerebral cortex(frontal lobe)

Limbic system

(emotional input)

Communication at

subconscious level

Hypothalamus

Overall integrationof ANS, the boss

Spinal cordUrination, defecation,

erection, and ejaculationreflexes

Brain stem(reticular formation, etc.)

Regulation of pupil size,respiration, heart, blood

pressure, swallowing, etc.

Hypothalamic Control


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Hypothalamic Control

Control may be direct or indirect (through thereticular system)

Centers of the hypothalamus control

Heart activity and blood pressure Body temperature, water balance, and endocrine

activity

Emotional stages (rage, pleasure) and biological

drives (hunger, thirst, sex)

Reactions to fear and the fight-or-flight system

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Ch 14 Lecture Outline