Nervous System POM

8/8/2019 Nervous System POM

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AlianzaParas

Casue

DarjaniFojas

TanZebaradami

Massoudi


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Nervous System

CNS PNS

Brain Cranial nerves SpinalNerve

Spinal Cord


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Somatic Nervous SystemSkeletal muscles

Autonomic Nervous SystemSympathetic

Fight or flight

Paras ympatheticRest and repair


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A neuron or nerve cell is the basic unit ofinformation processing and the building bloc k of the brain.

It processes and transmits information b y electrical and chemical signaling.


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is a center for receiving and sending nerveimpulses.is responsible for ma king proteins and usingenerg y for the maintenance and growth ofthe nerve cell.The vast majorit y of neuron cell bodies arewithin the central nervous s ystem, where

incoming messages are combined andoutgoing messages are produced.


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The dendrites of a neuron are branching,tubeli ke extensions of the cell bod y thatform a pattern resembling the limbs of a

tree.Most neuron cell bodies have about six maindendrites, each of which is two or threetimes as thic k as the axon of the cell.

Dendrites are specialized structures forreceiving impulses, mostl y from the axon ofanother neuron.


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Dendrites and axons donot quite touch eachother. In almost all cases,the y are separated b y anextremel y narrow spacecalled the s ynaptic cleft,over which nerveimpulses are transmitted.These places where oneneuron communicateswith another are calledsynapses.


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is a tubeli ke extension of a neuron cell bod y.is specialized to carr y messages. An axon of one neuron ma y haveenough branches to ma ke contact with as man y as 1,000 otherneurons.The structures commonl y called nerves are actuall y bundles of

axons l ying next to one another in a cordli ke formation.Nerves can be made up of the axons of motor neurons or sensor y neurons, or of both.Some axons are covered b y a sheath of a white, fatt y substancecalled m yelin which increases the speed of impulses along theaxons. M yelin also causes the distinction between the gre y matter and white matter in the nervous s ystem. Gre y matter

consists largel y of unm yelinated axons (axons without m yelinsheaths) and neuron cell bodies. White matter is made up mostl y of axons that have white sheaths of m yelin. M yelin is formed inthe peripheral nervous s ystem b y Schwann cells, which arespecial supporting cells that surround the axons. In the centralnervous s ystem, supporting cells called glia produce m yelin.


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consists of fat-containingcells that insulate theaxon from electricalactivit y. This insulationacts to increase the rateof transmission of signals.A gap exists between

each m yelin sheath cellalong the axon. Since fatinhibits the propagation

of electricit y, the signalsjump from one gap to thenext.


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The m yelin sheath (a tubular case or envelope) gives the whitishappearance to the white matter of the brain.It is included in the categor y of glial cells. Glial cells function tosupport the processes of neurons in a variet y of wa ys.The glial cells forming m yelin sheaths are called oligodendroc ytes

in the central nervous s ystem and Schwann cells in the peripheralnervous s ystem.The gaps (approximatel y 1micrometer wide) formed betweenmyelin sheath cells along the axons are called Nodes of Ranvier.Since fat serves as a good insulator, the m yelin sheaths speed therate of transmission of an electrical impulse along the axon. Theelectrical impulse jumps from one node to the next at a rate as

fast as 120 meters/second. This rapid rate of conduction is calledsaltator y conduction.Myelinated axons are rare in the autonomic nervous s ystem andabsent in the nervous s ystem of invertebrates.


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1. Astroc yte2. Microglia3. Eped ymal cell4. Oligodendroc yte5. Schwann cells


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Star shaped gliaFound onl y in the central nervous s ystemLargest and most numerous t ype of gliaTheir long, delicate points extend through thebrain tissue, attaching to both neurons and thetin y blood capillaries of the brain


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Feed the neurons b y pic king up glucose from theblood , converting it to lactic acidThen passing it along to the neurons to which the y are connectedThe webs of astroc ytes form tight sheath aroundthe brainHelps form the blood brain barrier (BBB)


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BBB is a double barrier made up of astroc ytefeetand the endothelial cells that ma ke up thewalls of the capillaries


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SmallUsuall y stationar y cells found in the centralnervous s ystemIn inflamed or degenerating brain tissue, microgliaenlarge more about and carr y on phagoc ytosisThe y engulf and destro y microorganism andcellular debris


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Resemble epithelial cells foming thin sheet thatline fluid filed cavities in the brain and spinal cordSome epend ymal cells ta ke part in the producing

the fluid that fills these spacesOthers have cilia that helps keep the fluidcirculating within the cavities


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Smaller than astroc yte and have fewer processesLiterall y means cell with few branches (oligo-,few; -dendro-, branch; -c yte, cell)

Some oligodendroc ytes lie clustered around nervecell bodiesSome are arranged in rows bet. nerve fibers in thebrain and cord


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The y help hold nerve fibers togetherAnd the y produce the fatt y myelin sheath aroundnerve fibers in the central nervous s ystem


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Found onl y in the peripheral nervous s ystemThe y serve as the functional equivalent of theoligodendroc ytes, supporting nerve fibers and

sometimes forming m yelin sheath around themThe y can wrap themselves around a single nervefiber


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microscopic gaps in the sheath, bet adjacentSchwann cells are called nodes of Ranvier

Myelin sheath is formed b y la yers of Schwann cell

membrane containing white, fatt y substancemyelinN eurilema orsheath of Schwann is essential tothe regeneration of injured nerve fibers


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Myelinated fibers or white fibers-nerve with man y Schwann cell forming a

thic k myelin sheathU nmyelinated fibers or gray fibers

-several nerve fibers are held b y a singleSchwann cell that does not wrap arround them toform thic k myelin sheath


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Satellite cell-t ype of Schwann cell, li ke satellites

positioned arround a planet

-special schwann cell bod y of a neuron-support neural cell bodies in regions called

ganglia in PN S


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The electric charge of the nerve when it isnot stimulated (-90mv)Membrane potential electrical charge of

the inside of the membrane relative to theoutside


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Rapid change in the membrane potentialthat spreads rapidl y along the nerve fiberStages

Resting stageDepolarizationRepolarization


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Strong stimulus ---> threshold--->actionpotentialWea k stimulus --->threshold ---> subthreshold

potential


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Is the part of the brain between the brainstem andthe cerebrum.

Its main components are the thalamus,epithalamus, and h ypothalamus.

Part of the brain inferior to and nearl y surrounded b y the cerebrum, and connectingposteriorl y and inferiorl y to the brainstem.


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Is the largest part of the diencephalon.

involved in the rela y of sensor y input tothe cerebrum.

a large mass of gra y matter ma king up thebul k of the diencephalons

it also influences mood and registers anunlocalized, uncomfortable perception ofpain.


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Is a small area superior and posterior to thethalamus.

consist of a few small nuclei that areinvolved in the emotional and viceralresponse to odors, and the pi neal body


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The e pith alamus is a dorsal posterior segment ofthe diencephalon (a segment in the middle of thebrain also containing the hypothalamus and thethalamus ) which includes the habenula , the striamedullaris and the pineal bod y

Its function is the connection between thelimbic s ystem to other parts of the brain.


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is a small endocrine gland in the vertebrate brain .

It produces the serotonin derivative melatonin , a hormonethat affects the modulation of wa ke/sleep patterns andseasonal functions.

Its shape resembles a tin y pine cone (hence its name),and it is located near the center of the brain, between thetwo hemispheres , tuc ked in a groove where the tworounded thalamic bodies join.


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originall y denoted the stal k of the pineal gland , butgraduall y came to refer to a neighb oring group of nerve cellswith which the pineal gland was believed to be associated,the habenular nucleus.

S t r ia Medullar is

is a fiber bundle containing efferent fibers from theseptal nuclei , lateral preoptico- hypothalamic region, andanterior thalamic nuclei to the habenula . It forms ahorizontal ridge on the medial surface of the thalamus .


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Is the most inferior part of the diencephalonand contains several small nuclei, which isver y important in maintaining homeostasis.

pla ys a central role in the control of bod y temperature, hunger, and thirst.

sensations such as sexual pleasure, feelingrelaxed and good after a meal, rage, and fearare related to h ypothalamic functions.


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Is the largest part of the brain.

it is divided into the left and righthemispheres b y a long it ud inal f issure.

The most conspicuous features on thesurface of each hemisphere are the numerousfolds called gyr i, which greatl y increases thesurface area of the cortex, and the

intervening grooves called sulc i.


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Lobes of the cerebrum:

Frontal lobe

Parietal lobe

Occipital lobe

Temporal lobe


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Is important in the control of voluntar y motorfunctions, motivation, aggression, mood, andolfactor y reception.

P ar ie t al lobe

is the principal center for the reception andconscious perception of most sensor y information, such as touch, pain,temperature, balance and taste.


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Functions in the reception and perception of visualinput and is not distinctl y separate from the otherlobes.

Tem poral lobe

Is involved in olfactor y and auditor y sensations and pla ys an important role inmemor y.


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Parts:MEDULLA OBLONGATA Heart

rate, Breathing, swallowing,balanceP ONS rela y between

cerebellum & cerebrum


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MIDBRAIN hearing & visualreflexes

RET ICULAR FORMAT ION regulating c yclical motorfunctions:

ConsciousnessSleep-wa ke c ycle


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Parts:THALAMUS - main sensor y

rela yEPITHALAMUS sexualmaturation

HYPOTHALAMUS - homeostasis


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2 hemispheres4 LOBES:FrontalParietalTemporaloccipital


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-contains preganglionic and

postganglionic neurons-DIVI SIONS:

-SYMPATHETIC-PARASYMPATHETIC


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Responsible for vegetative activities:Digestion, defecation, urination

Preganglionic cell bodies are associatedwith C RANIAL and SACRAL nerves

Postganglionic cell bodies lie inTERMINAL GANGLIA, near and within thetarget area


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Perpares the person for action b y:Increasing the heart rate, bloodpressure, respirator y rate

Preganglionic cell bodies lie in theTHORACIC & LUMBAR regions of the

spinal cordPostganglionic cell bodies lie in theSYMPATHETIC CHAIN GANGLIA or in theCOLLATERAL GANGLIA


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Continuation of the MEDULLA OBLONGATA of the brainstemsurrounded and protected b y the bon y vertebral column andby dis ks of fibrocatilage ( Intervertebral dis ks)surrounded b y a clear fluid called Cerebral Spinal Fluid (C SF)

C erebral Spinal Fluid acts as a cushion to protect the delicate nervetissues against damage from banging against theinside of the vertebrae.

protected b y the spinal meninges.Outermost spinal meninges DURA MATERMiddle spinal meninges ARACHNOID MATERInnermost PIA MATER


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transmit electrical information to and from the limbs, trun k andorgans of the bod y, bac k to and from the brain.

BRAIN + SPINAL CORD = C entral N ervous System

NERV ES SPINAL CORD BODY =P eripheral N ervous System.

Major Function:to conve y sensor y implulses from the peripher y to the brain and to

conduct motor impulse from the brain to the peripher y.

Ascend ing t rac t s within the spinal cord carr y information from thebod y, upwards to the brain such as touch, s kin temperature, painand joint position.

Descend ing t rac t s spinal cord carr y information from the brain downwards toinitiate movement and control bod y functions.


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There are four ma in grou ps of s pi nal nerves w hi ch

exit different levels of the spinal cord.Cerv ical Nerves "C" : (nerves in the nec k) suppl y movement and feeling to the arms, nec k and uppertrun k.T

horac ic Nerves "T

" : (nerves in the upper bac k)suppl y the trun k and abdomen.Lumbar Nerves "L" and Sacral Nerves " S" : (nervesin the lower bac k) suppl y the legs, the bladder,

bowel and sexual organs.


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A reflex arc is the neural pathwa y thatmediates a reflex action. In higher animals,most sensor y neurons do not pass directl y

into the brain, but s ynapse in the spinal cord.This characteristic allows reflex actions tooccur relativel y quic kly by activating spinalmotor neurons without the dela y of routingsignals through the brain, although the brainwill receive sensor y input while the reflexaction occurs.


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Rubber mullet is used. The knee jerk reflex is calleda monosynaptic reflexbecause there is only onesynapse in the circuit neededto complete the reflex. It onlytakes about 50 millisecondsbetween the tap and thestart of the leg kick. That isfast! The tap below the kneecauses the thigh muscle tostretch. Information is thensent to the spinal cord. Afterone synapse in the ventralhorn of the spinal cord, theinformation is sent back outto the thigh muscle that thencontracts


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Autonomic reflex arc (affecting inner organs)and Somatic reflex arc (affecting muscles).


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When a reflex arc consists of onl y two neurons in ananimal (one sensor y neuron, and one motor neuron),it is defined as monosyna pti c. Monos ynaptic refers tothe presence of a single chemical s ynapse. In the

case of peripheral muscle reflexes (patellar reflex)brief stimulation to the muscle spindle results incontraction of the antagonist or effector muscle.By contrast, in polysyna pti c reflex pathwa ys, one ormore interneurons connect afferent (sensor y) andefferent (motor) signals. All but the most simplereflexes are pol ysynaptic, allowing processing orinhibition of pol ysynaptic reflexes within the spinalcord.


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P a t ellar reflex : when the patellar tendon is tappedjust below the knee, the patellar reflex is initiatedand the lower leg kicks forward (via contraction ofthe quadriceps). The tap initiates an action potentialin a specialized structure known as a muscle spindle

located within the quadriceps. This action potentialtravels to the spinal cord, via a sensor y axon whichchemicall y communicates b y releasing glutamateonto a motor nerve. The result of this motor nerveactivit y is contraction of the quadricpes muslce,leading to extension of the lower leg at the knee.The sensor y input from the quadriceps also activateslocal interneurons that release the inhibitor y neurotransmitter gl ycine onto motor neurons,bloc king the innervation of the antagonistic(hamstring) muscle. The relaxation of the opposingmuscle facilitates extension of the lower leg.


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Inborn or in t r ins ic reflex - a reflex which is unlearned,involuntar y and in which the pathwa ys are built into thebod y of each individual during development.Learned or acqu ired reflex - a reflex which is learnedthrough practice and ma y involve both a far morecomplicated set of triggering stimuli and a far morecomplicated pattern of motor response, e.g., the reflexivemotor actions produced after one has learned to ride abic ycle or drive a car; most such reflexes are somaticbecause the y involve complex response patterns fromskeletal muscles.Spi nal reflex - The inborn reflexes mediated b y control

centers in the spinal cord; although the central pathwa y involve onl y spinal cord segment control.Cran ial reflexes - The inborn reflexes b y control centers inthe brain; the pathwa y usuall y involve cranial and cervicalspinal nerves


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Cranial nerves are nerves that emergedirectl y from the brain , in contrast tospinal nerves which emerge from

segments of the spinal cord . In humans,there are 12 pairs of cranial nerves. Onl y the first and the second pair emerge fromthe cerebrum ; the remaining 10 pairs

emerge from the brainstem .


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Olfactor y nervePurel y Sensor yAnterior olfactor y nucleus Transmits the sense of

smell; Located in olfactor y foramina in theCribriform plate of ethmoid


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Optic nervePurel y Sensor y Ganglion cells of retina [5] Transmits visual

information to the brain; Located in opticcanal


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Oculomotor nerveMainly MotoMidbrain

Innervates levator

palpebrae superioris ,superior rectus , medialrectus , inferior rectus , andinferior oblique , whichcollectivel y perform most

e ye movements;Located in superior orbitalfissure


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Trochlear nerveMainly MotorMidbrainInnervates the superioroblique muscle , whichdepresses, rotates laterall y (around the optic axis), and

the e yeball;Located in superior orbitalfissure


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Trigeminal nerveBoth Sensor y and MotorPons

Receives sensation from

the face and innervates themuscles of mastication ;Located in superior orbitalfissure (ophthalmic nerve -V1), foramen rotundum(maxillar y nerve - V2), andforamen ovale (mandibularnerve - V3)


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Abducens nerveMainly MotorInnervates the lateralrectus , which abductsthe e ye; Located insuperior orbital fissure


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Facial nerveBoth Sensor y and Motor

Provides motor innervation tothe muscles of facialexpression , posterior bell y ofthe digastric muscle, ,receives

the special sense of taste fromthe anterior 2/3 of the tongue ,and provides innervation to thesalivar y glands (except parotid)and the lacrimal gland ;Located and runs through

internal acoustic canal tofacial canal and exits atst ylomastoid foramen


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Vagus nerveBoth Sensor y and MotorSupplies branchiomotorinnervation to most lar yngeal andall phar yngeal muscles (exceptthe st ylophar yngeus , which isinnervated b y theglossophar yngeal);; and receivesthe special sense of taste fromthe epiglottis. A major function:controls muscles for voice andresonance and the soft palate.DAMAGE:dysphagia (swallowingproblems), velophar yngealinsufficienc y.Located in jugular foramen


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Vestibulocochlear nerveSenses sound, rotation andgravit y (essential for balance& movement). Morespecificall y. the vestibularbranch carries impulses forequilibrium and the cochlearbranch carries impulses for

hearing.;Located in internal acousticcanal


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Glossophar yngeal nerveBoth Sensor y and MotorReceives taste from the

posterior 1/3 of the tongue,provides secretomotorinnervation to the parotidgland , and provides motorinnervation to thest ylophar yngeus .. Located in jugular foramen


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Accessor y nerve (or cr aniala ccessory nerve or sp inala ccessory nerve )Mainly Motor Cranial and SpinalRootsControls sternocleidomastoid

and trapezius muscles, overlapswith functions of the vagus.

Examples of s ymptoms ofdamage: wea k head movement;Located in jugular foramen


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Hypoglossal nerveMainly MotorProvides motor innervation

to the muscles of the tongue(except for the palatoglossus ,which is innervated b y thevagus) and other glossalmuscles. Important for

swallowing (bolus formation)and speech articulation.Located in hypoglossal canal

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Nervous System POM