Anatomy Nervous System 1st Proff 2022-23.pdf

Anatomy Nervous System 1st Proff 2022-23.pdf

1. Nervous System
Pharm D 1
st
Prof
Bahauddin Zakariya University Multan
Waseem Ashraf

2. Recommended Books:
•Fundamentals of Anatomy & Physiology. Martini F, Nath JL, Bartholomew EF. 10th Edition
•Principles of Anatomy and Physiology. Tortora GJ, Derrickson B. 13th Edition

3. Nervous System
Thecentralnervoussystem(CNS)consistsofthebrainandspinalcord.
Theperipheralnervoussystem(PNS)includesalltheneuraltissueoutsidetheCNS.Bundlesofaxons,ornervefibers,
carrysensoryinformationandmotorcommandsinthePNS.Suchbundles,withassociatedbloodvesselsandconnective
tissues,arecalledperipheralnerves,orsimplynerves.
Nervesconnectedtothebrainarecalledcranialnerves,andthoseattachedtothespinalcordarecalledspinalnerves.
Brain
Theadulthumanbraincontainsalmost97percentofthebody’sneuraltissue.A“typical”brainweighs1.4kg(3lb)andhas
avolumeof1200ml(71in.3).Brainsizevariesconsiderablyamongindividuals.Thebrainsofmalesare,onaverage,about
10percentlargerthanthoseoffemales,duetodifferencesinaveragebodysize.Nocorrelationexistsbetweenbrainsizeand
intelligence.Individualswiththesmallestbrains(750ml)andthelargestbrains(2100ml)arefunctionallynormal.
Therearesixmajorbrainregions:
1.Cerebrum,
2.Diencephalon,
3.Midbrain,
4.Pons,
5.Medullaoblongataand
6.Cerebellum.

6. Nervous System
Cerebrum
ThelargestportionoftheadultbrainistheCerebrum.Itismadeupoflargepairedleftandrightcerebralhemispheres.
Thebrainhasanextensiveareaofcortex,asuperficiallayerofgraymattercoveringmostofitssurface.Thesurfacesofthe
cerebralhemispheresarehighlyfoldedandcoveredbyaneuralcortexcalledthecerebralcortex(cortex,rindorbark).This
cerebralcortexformsaseriesofelevatedridges,orgyri.Gyriincreaseitssurfacearea.Thegyriareseparatedbyshallow
depressionscalledsulciorbydeepergroovescalledfissures.Thecerebrumistheseatofmosthighermentalfunctions.
Consciousthoughts,sensations,intellect,memory,andcomplexmovementsalloriginateinthecerebrum.
Diencephalon
Thewallsofthediencephalonarecomposedoftheleftthalamusandrightthalamus.Eachthalamuscontainsrelayand
processingcentersforsensoryinformation.Thehypothalamus(hypo-,below)isthefloorofthediencephalon.Itcontains
centersinvolvedwithemotions,autonomicfunction,andhormoneproduction.
Theinfundibulum,anarrowstalk,connectsthehypothalamustothepituitarygland,apartoftheendocrinesystem.The
hypothalamusandthepituitaryglandintegratethenervousandendocrinesystems.
Thediencephalonisastructuralandfunctionallinkbetweenthecerebralhemispheresandthebrainstem.

7. BrainStem(Midbrain,Pons,andMedullaoblongata)
Thebrainstemcontainsavarietyofimportantprocessingcentersandnucleithatrelayinformationheadedtoorfromthe
cerebrumorcerebellum.Thebrainstemincludesthemidbrain,pons,andmedullaoblongata.
MidBrain
Themidbrain,ormesencephalon,containsnucleithatprocessvisualandauditoryinformationandcontrolreflexestriggered
bythesestimuli.Forexample,yourimmediate,reflexiveresponsestoaloud,unexpectednoise(eyemovementsandhead
turning)aredirectedbynucleiinthemidbrain.Thisregionalsocontainscentersthathelpmaintainconsciousness.
Pons
Theponsofthebrainconnectsthecerebellumtothebrainstem(ponsislatinfor“bridge”).Inadditiontotractsandrelay
centers,theponscontainsnucleiinvolvedwithsomaticandvisceralmotorcontrol.
MedullaOblongata
Themedullaoblongataconnectsthebraintothespinalcord.Nearthepons,theposteriorwallofthemedullaoblongatais
thinandmembranous.Theinferiorportionofthemedullaoblongataresemblesthespinalcordinthatithasanarrowcentral
canal.Themedullaoblongatarelayssensoryinformationtothethalamusandtocentersinotherportionsofthebrainstem.
Themedullaoblongataalsocontainsmajorcentersthatregulateautonomicfunction,suchasheartrate,bloodpressure,and
digestion.

8. Cerebellum
Thecerebellum(ser-e-BEl-um)isthesecond-largestpartofthebrain.Itispartiallyhiddenbythecerebralhemispheres.like
thecerebrum,thecerebellumhashemispherescoveredbyaneuralcortexcalledthecerebellarcortex.

10. Ventricles of the Brain
Duringdevelopment,theneurocoelwithinthecerebralhemispheres,diencephalon,metencephalon,andmedullaoblongata
expandstoformchamberscalledventricles.Cellsoftheependymalinetheventricles.
Eachcerebralhemispherecontainsalargelateralventricle.Theseptumpellucidum,athinmedialpartition,separatesthe
twolateralventricles.Becausetherearetwolateralventricles,theventricleinthediencephaloniscalledthethird
ventricle.Thetwolateralventriclesarenotdirectlyconnected,buteachcommunicateswiththethirdventricleofthe
diencephalonthroughaninterventricularforamen(foramenofMonro).
Themidbrainhasaslendercanalknownasthecerebralaqueduct.Thispassagewayconnectsthethirdventriclewiththe
fourthventricle.Thesuperiorportionofthefourthventricleliesbetweentheposteriorsurfaceoftheponsandtheanterior
surfaceofthecerebellum.Thefourthventricleextendsintothesuperiorportionofthemedullaoblongata.Therethis
ventriclenarrowsandbecomescontinuouswiththecentralcanalofthespinalcord.
Theventriclesarefilledwithcerebrospinalfluid(CSF).TheCSFcontinuouslycirculatesfromtheventriclesandcentral
canalintothesubarachnoidspaceofthesurroundingcranialmeninges.TheCSFpassesbetweentheinteriorandexteriorof
theCNSthroughthreeforaminaintheroofofthefourthventricle.

12. Cranial Meninges
Cranialmeningesaremadeupof—thecranialduramater,arachnoidmater,andpiamaterwhicharecontinuouswith
thespinalmeninges.However,thecranialmeningeshavedistinctiveanatomicalandfunctionalcharacteristics.
DuraMater
Theduramaterconsistsofouterandinnerfibrouslayers.Theouterlayerisfusedtotheperiosteumofthecranialbones.As
aresult,thereisnoepiduralspacesuperficialtotheduramater,asoccursalongthespinalcord.Theouter,periosteal,and
inner,meningeal,layersofthecranialduramateraretypicallyseparatedbyaslendergapthatcontainstissuefluidsand
bloodvessels,includingseverallargevenoussinuses.Theveinsofthebrainopenintothesesinuses,whichdeliverthe
venousbloodtotheinternaljugularveinsoftheneck.
ArachnoidMater
Thearachnoidmaterconsistsofthearachnoidmembrane(anepitheliallayer)andthecellsandfibersofthearachnoid
trabeculaethatcrossthesubarachnoidspacetothepiamater.Thearachnoidmembranecoversthebrain,providinga
smoothsurfacethatdoesnotfollowthebrain’sunderlyingfolds.Thismembraneisincontactwiththeinnerepitheliallayer
oftheduramater.Thesubarachnoidspaceextendsbetweenthearachnoidmembraneandthepiamater

13. Cranial Meninges
PiaMater
Thepiamaterstickstothesurfaceofthebrain,anchoredbytheprocessesofastrocytes.Itextendsintoeveryfoldand
fissure.Italsoaccompaniesthebranchesofcerebralbloodvesselsastheypenetratethesurfaceofthebraintoreachinternal
structures.
DuralFolds
Inseverallocations,theinnerlayeroftheduramaterextendsintothecranialcavity,formingasheetthatdipsinwardand
thenreturns.Theseduralfoldsprovideadditionalstabilizationandsupporttothebrain.Duralsinusesarelargecollecting
veinslocatedwithintheduralfolds.Thethreelargestduralfoldsarecalledthefalxcerebri,thetentoriumcerebelli,and
thefalxcerebelli:
1.Thefalxcerebri(falx,curvingorsickleshaped)isafoldofduramaterthatprojectsbetweenthecerebralhemispheresin
thelongitudinalfissure.Itsinferiorportionsattachanteriorlytothecristagallioftheethmoidboneandposteriorlytothe
internaloccipitalcrest,aridgealongtheinnersurfaceoftheoccipitalbone.Thesuperiorsagittalsinusandtheinferior
sagittalsinus,twolargevenoussinuses,liewithinthisduralfold.Theposteriormarginofthefalxcerebriintersectsthe
tentoriumcerebelli.

14. Cranial Meninges
2.Thetentoriumcerebelli(tentorium,tent)protectsthecerebellumandseparatesthecerebralhemispheresfromthe
cerebellum.Itextendsacrossthecraniumatrightanglestothefalxcerebri.Thetransversesinuslieswithinthetentorium
cerebelli.
3.Thefalxcerebellidividesthetwocerebellarhemispheresalongthemidsagittallineinferiortothetentoriumcerebelli

18. Major Areas of Brain
MedullaOblongata

19. Major Areas of Brain
Pons

20. Major Areas of Brain
Cerebellum

21. Major Areas of Brain
Cerebellum

22. Major Areas of Brain
Midbrain

23. Major Areas of Brain
Midbrain

24. Major Areas of Brain
Diencephalon/Thalamus

25. Major Areas of Brain
Diencephalon/Hypothalamus

26. Major Areas of Brain
Diencephalon/Hypothalamus

36. Oh, Once One Takes The
Anatomy Final, Very
Good Vacations Are
Heavenly

37. GROSS ANATOMY OF THE SPINAL CORD
The adult spinal cord is approximately 45 cm (18 in.) long, with a maximum width of roughly 14 mm (0.55 in.). Note that the
cord itself is not as long as the vertebral column. Instead, the adult spinal cord ends between vertebrae L1 and L2.
Theposterior(dorsal)surfaceofthespinalcordhasashallowlongitudinalgroove,theposteriormediansulcus.The
anteriormedianfissureisadeepergroovealongtheanterior(ventral)surface.
The amount of gray matter is greatest in segments of the spinal cord dedicated to the sensory and motor control of the limbs.
These segments are expanded, forming the enlargementsof the spinal cord.
The cervical enlargement supplies nerves to the shoulder and upper limbs. The lumbar enlargement provides innervation
to structures of the pelvis and lower limbs.
Inferior to the lumbar enlargement, the spinal cord becomes tapered and conical. This region is the conus medullaris. The
filum terminale(“terminal thread”), a slender strand of fibrous tissue, extends from the inferior tip of the conus medullaris.
It continues along the length of the vertebral canal as far as the second sacral vertebra, where it provides longitudinal support
to the spinal cord as a component of the coccygeal ligament.
The entire spinal cord can be divided into 31 segments on the basis of the origins of the spinal nerves.

38. Everyspinalsegmentisassociatedwithapairofdorsalroot
ganglia,locatednearthespinalcord.
Thesegangliacontainthecellbodiesofsensoryneurons.The
axonsoftheneuronsformthedorsalroots,whichbringsensory
informationintothespinalcord.
Apairofventralrootscontainstheaxonsofmotorneuronsthat
extendintotheperipherytocontrolsomaticandvisceraleffectors.
Onbothsides,thedorsalandventralrootsofeachsegmentpass
betweenthevertebralcanalandtheperipheryatthe
intervertebralforamenbetweensuccessivevertebrae.Thedorsal
rootganglionliesbetweenthepediclesoftheadjacentvertebrae.
Distaltoeachdorsalrootganglion,thesensoryandmotorroots
areboundtogetherintoasinglespinalnerve.
Spinalnervesareclassifiedasmixednerves—thatis,theycontain
bothafferent(sensory)andefferent(motor)fibers.

41. ORGANIZATION OF THE SPINAL CORD
Together,theanteriormedianfissureandtheposteriormediansulcusdividethespinalcordintoleftandrightsides.
ThegraymatterformsanHorbutterflyshapeandsurroundsthenarrowcentralcanal.
Hornsaretheareasofgraymatteroneachsideofthespinalcord.Thegraymatterisdominatedbythecellbodiesof
neurons,neuroglia,andunmyelinatedaxons.Thesuperficialwhitemattercontainslargenumbersofmyelinatedand
unmyelinatedaxons.

42. ORGANIZATION OF THE GRAY MATTER
Afrontalsectionalongthelengthofthecentralcanalofthespinalcordseparatesthesensory(posterior,ordorsal)nuclei
fromthemotor(anterior,orventral)nuclei.Theposteriorgrayhornscontainsomaticandvisceralsensorynuclei,and
theanteriorgrayhornscontainsomaticmotornuclei.Thelateralgrayhorns,locatedonlyinthethoracicandlumbar
segments,containvisceralmotornuclei.
Thegraycommissures(commissura,ajoiningtogether)posteriortoandanteriortothecentralcanalcontainaxonsthat
crossfromonesideofthecordtotheotherbeforetheyreachanareainthegraymatter.

44. ORGANIZATION OF THE WHITE MATTER
Thewhitematteroneachsideofthespinalcordcanbedividedintothreeregionscalledcolumns,orfuniculi(Figure13–
5a).Theposteriorwhitecolumnsliebetweentheposteriorgrayhornsandtheposteriormediansulcus.
Theanteriorwhitecolumnsliebetweentheanteriorgrayhornsandtheanteriormedianfissure.Theanteriorwhite
columnsareinterconnectedbytheanteriorwhitecommissure,aregionwhereaxonscrossfromonesideofthespinalcord
totheother.
Thewhitematterbetweentheanteriorandposteriorcolumnsoneachsidemakesupthelateralwhitecolumn.
Eachcolumncontainstractswhoseaxonssharefunctionalandstructuralcharacteristics.Atract,orfasciculus(bundle),
isabundleofaxonsintheCNSthatissomewhatuniformindiameter,myelination,andpropagationspeed.
Alltheaxonswithinatractrelaythesametypeofinformation(sensoryormotor)inthesamedirection.Shorttracts
carrysensoryormotorsignalsbetweensegmentsofthespinalcord,andlongertractsconnectthespinalcordwiththe
brain.Ascendingtractscarrysensoryinformationtowardthebrain,anddescendingtractsconveymotorcommandsto
thespinalcord.

46. Anatomy of Spinal Nerves
Everysegmentofthespinalcordisconnectedtoapairofspinalnerves.Surroundingeachspinalnerveisaseriesof
connectivetissuelayerscontinuouswiththoseoftheassociatedperipheralnerves.
Theselayers,bestseeninsectionalview,arecomparabletothoseassociatedwithskeletalmuscles.
Theepineurium,oroutermostlayer,consistsofadensenetworkofcollagenfibers.Thefibersoftheperineurium,the
middlelayer,extendinwardfromtheepineurium.Theseconnectivetissuepartitionsdividethenerveintoaseriesof
compartmentsthatcontainbundlesofaxons,orfascicles.
Delicateconnectivetissuefibersoftheendoneurium,theinnermostlayer,extendfromtheperineuriumandsurround
individualaxons.
Arteriesandveinspenetratetheepineuriumandbranchwithintheperineurium.Capillariesleavingtheperineurium
branchintheendoneurium.TheysupplytheaxonsandSchwanncellsofthenerveandthefibroblastsoftheconnective
tissues.
Asthespinalnervesextendintotheperiphery,theybranchandinterconnect,formingtheperipheralnervesthatinnervate
bodytissuesandorgans.Theconnectivetissuesheathsofperipheralnervesarethesameas,andcontinuouswith,thoseof
spinalnerves.

48. TheAutonomicNervousSystemisinvolvedintheunconsciousregulationofvisceralfunctionsandhas
SYMPATHETIC andPARASYMPATHETIC divisions.
Bothsomaticandautonomicnervoussystemsareefferentdivisionsthatcarrymotorcommands.TheSNScontrols
skeletalmuscles,andtheANScontrolsvisceraleffectorssuchassmoothmuscle,glands,cardiacmuscle,and
adipocytes.
TheprimarystructuraldifferencebetweenthetwoisthatintheSNS,motorneuronsofthecentralnervoussystemexert
directcontroloverskeletalmuscles.IntheANS,bycontrast,motorneuronsofthecentralnervoussystemsynapseon
visceralmotorneuronsinautonomicganglia,andtheseganglionicneuronscontrolvisceraleffectors.
Thehypothalamuscontainstheintegrativecentersforautonomicactivity.Theneuronsinthesecentersarecomparable
totheuppermotorneuronsintheSNS.Visceralmotorneuronsinthebrainstemandspinalcordareknownas
preganglionicneuronsbecausetheyextendtoganglia.Theseneuronsarepartofvisceralreflexarcs.Mostoftheir
activitiesrepresentdirectreflexresponses,ratherthanresponsestocommandsfromthehypothalamus.Theaxonsof
preganglionicneuronsarecalledpreganglionicfibers.
Autonomic Nervous System

49. PreganglionicfibersleavetheCNSandsynapseonganglionicneurons—visceralmotorneuronsinperipheralganglia.
Theseganglia,whichcontainhundredstothousandsofganglionicneurons,arecalledautonomicganglia.Ganglionic
neuronsinnervatevisceraleffectorssuchassmoothmuscle,glands,cardiacmuscle,andadipocytes.Theaxonsof
ganglionicneuronsarecalledpostganglionicfibers,becausetheybeginattheautonomicgangliaandextendtothe
peripheraltargetorgans.