Nervous System Anatomy and Physiology Lecture

8/18/2019 Nervous System Anatomy and Physiology Lecture

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The Nervous System

The nervous system coordinatesall body functions enabling aperson to adapt to changes in

internal and e!ternal environment The nervous system is composedmainly of the nerve cells "neurons#

and supporting cells "neuroglia#


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The neuron

This is the basicconducting cell of thenervous systemHighly specialized butcannot reproduce itself Main parts are the cell

body (soma), the bers:axon and dendrites


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The neuron

The axon is a long process!ith myelin sheath Thisconducts impulses a!ay fromthe cell body

The dendrites are short, thic",di#use branching processesthat receive impulses andconduct them to!ards the cellbody


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The $%&'$

The nervoussystem iscomposed ofneurons which

produce andconductelectrochemicalimpulses andsupporting

cells whichassist thefunctions ofneurons.


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The neuroglia

The supporting cellsThey supply nutrients to theneurons and help maintain theelectrical potentialThey also form part of the bloodbrain barrierThey are made up of macroglia,microglia and ependymal cells


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The neuroglia

ligodendrocytes producemyelin sheath in the *$

+c!hann cells or lemmocytesproduce myelin sheath in theperipheral $+


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The Organi$ation of the NervousSystem

The nervous system is dividedfunctionally and structurallyinto % parts&. 'entral Nervous System( the)rain and the spinal cord

%. Peripheral Nervous System(the cranial nerves and spinalnerves


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The Organi$ation of the nervousSystem

The Peripheral Nervous System isfurther classi*ed into T+,--unctional /ivisions

&. The Somatic Nervous System(controls the s0eletal muscles%. The Autonomic Nervous System(controls the visceral organs1. The -nteric Nervous System(controls the functions of the 23T


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The 'entral Nervous System

'omposed of the brain The brain consists of the grossstructures4 cerebrum cerebellum

brainstem and the diencephalon./iencephalon( Thalamus.+ypothalamus and pineal body

)rainstem( Pons medulla andMidbrain


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)rain)rain

*ortex

*orpus callosum

+eptum pelluciduornix

ThalamusHypothalamus

ptic chiasmaHypophysis

-rd ventricle

.th ventricle

*erebellum

/rain stem

+pinal cord


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The 'erebrum

This is the largest part of the brain'onsists of right and left hemisphereconnected by the corpus callosum

-ach cerebral hemisphere iscomposed of di5erent lobes( frontaltemporal parietal and occipital-mbedded in the cerebrum is the

)ASA6 ganglia


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The rontal 6obe of thecerebrum

3n7uences thepersonality of theperson

Also responsible for

8udgment abstractreasoning socialbehavior languagee!pression and motor

movement.


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The Temporal lobe of the'erebrum

This part of thecerebrum controls thehearing, languagecomprehension,storage and recall ofmemories

The 01M/1* system isdeeply located in thetemporal lobe This

controls the basicdrives such as hunger,anger, emotion andsexual drive


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The Parietal lobe of thecerebrum

This is the principalcenter for thereception andinterpretation of

+ensationThis part interpretsand integrates thesensory inputs li"e

touch, temperatureand pain1t interprets size,

shape, distance andtexture


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The occipital lobe of thecerebrum

Thisfunctionsmainly tointerpretvisual stimuli


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+peech areas in thecerebrum

2 3ernic"e4s area responsiblefor the sensory reception ofspeech

5/roca4s 6rea responsible forthe motor speech


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The *erebellum

The second largest brain region+as also two hemispheresunctions to maintain muscle tone

coordinate muscle movement postureand control balance9e:uilibrium3f this is damaged muscle tonedecreases and *ne motor movements

become very clumsy


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The /rainstem

6ies inferior to the cerebrum'ontinuous with the cerebrum andthe spinal cord

3t is composed of the midbrain thepons and the medulla oblongata

unctions4 houses the center for

respiration and cardiovascularsystem


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The Midbrain

This connects with thecerebrum

'ontains numerousascending and descendingtracts and *bers


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The 7ons'onnects the cerebellumwith the cerebrum

+ouses the respiratorycenter and cardiovascularcenter

-!it points for cranial nerves; < and =


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The Medulla oblongata

The most inferior portion of thebrainstemServes as the center for autonomic

re7e!es to maintain homeostasisregulating respiratory vasomotorand cardiac functions

Serves as e!it of cranial nerves>&?&& and &%


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The 8iencephalon The thalamus and the

hypothalamus

The thalamus is the relaystation of all sensorystimuli towards the brain

The hypothalamus

controls bodytemperature appetitewater balance pituitarysecretions and sleep(wa0e cycle


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)rain circulation4 The circle of@illis


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The spinal cord

A long cylindrical structure e!tendingfrom the foramen magnum to the 6&in adult 6196 in pedia3n the cross section of the spinal cord

we *nd the 2,AY matter( containsneuronsB and @+3T- matter(consistsof nerve *bers There are 1& pairs of spinal nerves

that e!it the spinal cord


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The spinal cord

-ach spinal nerve is formed bythe dorsal root "sensory# andthe ventral root "motor#

'ervical segmentsC D pairs Thoracic segmentsC&% pairs6umbarC ; pairsSacralC; pairs'occygealC& pair


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The Meninges

These are 1 connective tissue layerssurrounding the brain and spinal cord.

&. /E,A MAT-,( the super*cial thic0estlayer. The area above the dura mater is

called epidural space%. A,A'+NO3/( second layer thin and wispy.

1. P3A MAT-,( the deepest layer adhered to

the brain and spinal cord substance


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The Meninges The space in between

the arachnoid and piamater is called thearachnoid space

This arachnoid spacecontains the cerebro(spinal 7uid "'S#

3n this space blood

vessels are also found


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The 9entricles

These are 'S *lled cavities in thebrain

The lateral ventricle( found in the

cerebrum The third ventricle( in the center ofthe thalamus and hypothalamus

The fourth ventricle( located at thebase of the cerebellum


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The *+

This is the 7uid found inside theventricles that bathe the brain andspinal cord

unction4 provides protectivecushion around the 'NS

Produced by the choroid ple!us in

the ventriclesAbsorbed by the arachnoidgranulations


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Tracing the *+ path!ay

6ateral ventricle 3nterventricularforamen of Monro Thirdventricle 'erebral a:ueduct ofSylvius fourth ventricle e!its trough the median foramen ofMagendie or the lateral foramen of6usc0a Subarachnoid spaces in

the cisterna magna spinal cord subarachnoid space of the brain superior sagittal sinus


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The cranial nervesAre &% pairs of nerves that e!itthe brain

'an be classi*ed as

Sensory

Motor mi!ed "sensory and

motor#


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The 6utonomic $ervous+ystem The part of the peripheralnervous system that innervatescardiac muscles smooth

muscles and glandsunctionally divided into

Sympathetic Nervous System

Parasympathetic NervousSystem


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The +M76TH%T1* system

Originates from the T&(6%961segments of the spinal cord"thoracolumbar#

Etili$ed by the body for 632+Tand 32+T responseNeurotransmitter agents are

-pinephrine and Norepinephrine"coming from the adrenal gland#A/,-N-,23' system


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+ympathetic nervous system+ympathetic nervous system

T1

T2

T3

T4

T5

T6

T7

T8

T9

T10

T11

T12

L1

L2

L3

Pupils

Salivary glands

Heart

Brn!"i # lungs

Liver

St$a!"

S$all intestines

%drenal gland

&idneyLarge intestine

'e!tu$

Bladder

(enitals


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+ympathetic responses

/ecreasedPeristalsisSalivary secretions

-8aculation


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7arasympathetic +ystem

*H01$%';1* system

The vegetative system

eed and /reed responses*raniosacral location

*ranial nerves -, and +5+.

$eurotransmitter is 6cetylcholine


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7arasympathetic7arasympathetic

nervous systemnervous system Pupils

Salivary glands

Heart

Brn!"i # lungs

Liver

St$a!"

S$all intestines

Large intestine

'e!tu$

Bladder

(enitals


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7arasympathetic'esponses

3ncreased;astric secretions+alivary secretions

peristalsisPupillary constriction

/ecreased

Smooth muscle tone

sphincters are rela!ederection


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Nerve Physiology

The nerve cells are e!citable cellsAny stimulus will change themembrane potential and cause anaction potential to generate impulsetransmission or action potential The myelin sheath of the nerve cell isresponsible for the SA6TATO,Yconduction increases the nervetransmission


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A'T3ON POT-NT3A6

The synchroni$ed opening and closing ofNaF and G Fgates result in the movementof electrical charges that generates anerve impulse or action potential.

Action potentials reach the end of eachneuron where these electrical signalsare either transmitted directly to thene!t cell in the se:uence via gap

8unctions or are responsible foractivating the release of speciali$edneurotransmitter chemicals.


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TerminologiesAction potential H another name for Ispi0eJ potential

or nerve impulse/epolari$ation H upward oscilloscope de7ection or

NaF conductance is highest "hypopolari$ation#All(or(None is when the action potential amplitude

never varies

,epolari$ation H at this point NaF conductance isfalling rapidly and G F conductance has pea0ed.

Absolute refractory period H time of depolari$ation"NaF gates open#

,elative refractory period H time of depolari$ation"G Fgates open#

+yperpolari$ation H downward oscilloscopede7ection below resting


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6*T1$ 7T%$T160 6T


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6*T1$ 7T%$T160 6T+$67+%+

-lectrical synapsesbetween e!citablecells allow ions to

pass directly fromone cell to anotherand are muchfaster than

chemical synapses

An action potential at one node of ,anvier


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An action potential at one node of ,anviercauses inwards currents that move down thea!on depolari$ing the membrane and

stimulating a new action potential at the ne!tnode of ,anvier.


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3hat is saltatory conduction?6n action potential at one node of 'anvier

causes in!ards currents that move do!n theaction, depolarizing the membrane andstimulating a ne! action potential at the next

node of 'anvier


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The +$67+%

This is the region wherecommunication occurs between %neurons or between a neuron and a

target cellA neurotransmitter is releasedfrom the nerve cell towards the

other cell with receptor


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'e@ex 6rc The re7e! arc is a hard wired unconscious rapidresponse to e!ternal stimulus involving spinalnerves and e5ector cell.A re7e! is an automatic involuntary response of anorganism to a stimulus.

The entire nervous system is composed of

innumerable re7e! arcs.


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'%0%A%+ 1$ M6$


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+tretch re@ex

)iceps re7e! K ,adial ulnar


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)iceps re7e! K ,adial(ulnarre7e!

3hat is synaptic


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3hat is synaptictransmissionLSynaptic transmission is the process by

which nerve cells communicate amongthemselves and with muscles and glands.

The synapse is the anatomic site where this

communication occurs.Most synaptic transmission is carried out by

a chemical called a neurotransmitter.


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The neurotransmitter ismanufactured by the neuron andstored in vesicles at the axon

terminals

@hen the action potential reaches the a!on


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@hen the action potential reaches the a!onterminal it causes the vesicles to releasethe neurotransmitter molecules into thesynaptic cleft.

Th t itt di# th


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The neurotransmitter di#uses across thecleft and binds to receptors on the postsynaptic cleft cell

Then the activated receptors causechanges in the activity of the postsynapticneuron

The neurotransmitter molecules are


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The neurotransmitter molecules arereleased from the receptors anddi#use bac" into the synaptic cleft

The neurotransmitter is reabsorbed


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The neurotransmitter is reabsorbedby the post synaptic neuron Thisprocess is "no!n as reupta"e


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$eurotransmitters


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Physiology of ision

6ight waves travel at a speed of &D


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The eye and the visualpath!ay

ision is made possible by the stimulationof the photoreceptor cells in the retina

,eceptor cells are the ,O/S and 'ON-S

The eye is made up of three layersibrous layer( sclerae and corneaEvea( choroid and iris and ciliary bodiesNervous coat( retina


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unctions of the 7arts of

http://rds.yahoo.com/S=96062883/K=+anatomy+of+the+eye/v=2/SID=w/l=IVI/*-http://individual.utoronto.ca/yousef/images/eye.jpg


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unctions of the 7arts ofthe %ye

6ens H refraction and focusing3ris H regulated light entrancePupil H opening in the iris'horoid H absorbs stray lightSclera H for protection'ornea H refraction of light'iliary body H holds lens in place,etina H contains receptors "rods and cones#,ods H for blac0 and white vision

'ones H for color visionOptic nerve H transmits impulse'iliary muscle H for accommodation


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The optic nerve

This is the collection of *bersfrom the cells in the retina

3t passes through thebrainstem as the optic chiasm

it will reach the occipital

lobe for visual interpretation


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%MM%T'716 %mmetropia is normal

vision

7arallel light rays fromdistant obBects are insharp focus on theretina !hen the ciliarymuscle is completelyrelaxed

This means that theeye can see all distantobBects clearly, !ithits ciliary muscle

relaxed, but to focusobBects at close rangeit must providevarious degrees ofaccommodation


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Myopia

Myopia or nearsightedness results from ana!ial length of the eye that is too long forthe refractive power of the eye.

3n this case the focal point is in front of the

retina thus distant ob8ects cannot befocused on the retina.An ob8ect can be seen clearly if it is moved

closer to the eye so that the image forms inthe retina.


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+yperopia resultsfrom an a!ial

length of the eyethat is too shortfor the refractive

power of the eye.

3n this casedistant ob8ectscannot be focused

clearly becausethe focal point isat the bac0 of theretina.


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6stigmatism or6stigmatism or

Cghost visionD isCghost visionD is

!hen both far and!hen both far andnear obBectsnear obBects

appear out ofappear out of

focus This isfocus This is

because of thebecause of theuneven diameteruneven diameter

of the corneaof the cornea

(oblongshaped)(oblongshaped)

or light rays toor light rays to

focus precisely onfocus precisely on

the retina, thethe retina, the

cornea usuallycornea usually


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ovea E Macula

ovea centralis isan oval yellowisharea with adepression where

there are only conecells.


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+ize of the 7upils

Pupil si$e in7uences accommodation bycontrolling the amount of light enteringthe eye. 3n a bright light the pupils areconstricted. 3n a dim light they are dilated.

'ontraction of the circular *bers constricts

the pupil and contraction of the radiating*bers dilate it.

The si$e of the pupil is controlled bynerves of the ANS. Sympatheticstimulation dilates the pupils andparasympathetic stimulation causesconstriction.

3hat is 'hodopsin?


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3hat is 'hodopsin?,hodopsin or visual

purple is aphotosensitivepigment present onlyin the rods. 3t isbleached by brightlight and when this

occurs the rods cannot be stimulated.,hodopsin is :uic0ly

reconstituted when anade:uate supply of itA is available.

The rate at which dar0adaptation ta0es placeis dependent upon therate of reconstitutionof rhodopsin.


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7H+10; H%6'1$;


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+ow are sounds heardL

Sound waves cause movements of thetympanic membrane and thesemovements are both conveyed andampli*ed by the middle ear ossicles

"malleus incus and stapes#. The vibrations transmitted to the ossiclescause the foot plate of the stapes tovibrate against the oval window thereby

transmitting them to the inner ear. Thus air(borne sound waves aretransferred to the 7uid in the inner ear.


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The 9estibular apparatus

This is the part of the ear thathelps in e:uilibrium6ocated in the inner ear

The saccule and utricle control63N-A, motion The semicircular ducts controlthe Angular movement9acceleration


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7hysiology of +mell The sense of smell is

perceived when odorousmaterials in the air arecarried into the noseand stimulate the

olfactory cells.Perception of odor

decreases andeventually ceases dueto smell adaptation

The sense of smell maya5ect the appetite


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The lfactory apparatus

Stimulation from the olfactorynerves will reach the limbicsystem of the brain

'onsists of the nose and theolfactory nerve


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7rimary +mell E dor


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y+ystem

< primary types of

smellragrant

PutridSpicy,esinous)urnt

-theral

7 )dr Syste$7 )dr Syste$

*a$p"ra!eus*a$p"ra!eus

+us,y+us,y -lral-lral

+inty+inty

.t"eral.t"eral PungentPungent

PutridPutrid

7H+10; T6+T%


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7H+10; T6+T%

Th ;


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The ;ustatory apparatus

The receptor for taste arecells in the tongue group

together called the tastebudsThey are numerous in the

vallate and fungiformpapillae

Th 2 t t t


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The 2ustatory apparatus

/asic taste modalities+!eet tip of the tongue

+alty over the dorsum of thetongue+our sides of the tongue

/itter bac" of the tongue


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H t t i dL


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Ho! are taste perceivedL

Taste buds which consist of small bundlesof cells and nerve endings of cranial nerves"33 3 and #.

The nerve cells are stimulated by chemicalsubstances in solution that enter the pores.

The nerve impulses are transmitted to thethalamus then to the taste area in thecerebral corte! one in each hemispherewhere taste is perceived.

fundamental sensations of taste havebeen described4 sweet sour bitter andsalty.

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Nervous System Anatomy and Physiology Lecture