Download 7. The Nervous System Identify the major structures and areas of the

7.TheNervousSystem
Identifythemajorstructuresandareasofthebrainanddescribetheirfunctions
Thebrainiscomprisedofthreemainparts:
1. Forebrain
o Cerebralhemispheres
§ Largestpartofbrainandmaintainsmuscletone,coordinatesmovementandstores
memoriesofskilledmovemente.g.walkinganddriving
§ Fourlobes–frontal,parietal,occipital,temporal
§ Dividedintotwohalvesbyafurrow
§ Corpuscallosumisthebundleofaxonsconnectingthetwohemispheres
§ Greysurfacemadeofnervecells
§ Whitenervefibresunderneathcarrysignalsbetweennervecellsandrestofthebody
o Thalamus
§ Axonsfromeverysensorysystemsynapseherebeforetheinformationreachesthe
cerebralcortex
o Hypothalamus
§ Involvesinhomeostasis,emotion,thirst,hungeretc.
§ Controlsthepituitarygland
o Pinealandpituitarygland
2. Midbrain
o Fibretractsconnectingthe
forebraintomidand
hindbrainandcolliculi
3. Hindbrain
o Cerebellum(‘littlebrain’)
§ Twohemispheres
o Brainstem
§ Underneaththelimbic
system
§ Containsthemidbrain,
ponsandmedulla
o Pons
§ Involvedinmovement
andposture
o Medulla
§ Responsiblefor
maintainingvitalbodyfunctionsi.e.breathingandheartrate
Centralnervoussystem(CNS)–spinalcord&brain
Peripheralnervoussystem(PNS)–everythingelse
Structures
• Meninges:protectivemembranessurroundingthebrain
andspinalcordandspaceswithinthemcontainafluid
calledcerebrospinalfluid(CSF)
o CSFproducedbychoroidplexuscellsinthe
ventricles
• CSF:cushionsandprotectstheCNS,actsasamediumfor
theexchangeofnutrientsandwasteproductsbetween
thebloodandthebrain
• Foramenmagnum:divisionbetweenthebrainandspinalcord
• Intervertebralforamen:divisionbetweenthePNSandCNS
Ventriclesofthebrain
Brainregion
Thecavitywithineachofthecerebralhemispheres
Surroundedbythethalamusandhypothalamus
Betweenthemedullaandcerebellum
Ventricle
Lateral
Third
Fourth
Describethestructureofthespinalcord
Structure
Ventralroot
Dorsalroot
Dorsalrootganglion
Spinalnerve
Whitematter
Motoraxons
Sensoryfibres
Inthegreymatteroftheanterior
hornsinthespinalcord
Description
Containsnervefibresconductingimpulsesfromthespinalcord
Containsnervefibresconductingimpulsestothespinalcord
Containscellbodiesofsensoryneurons
Peripheralnervecontainingbothsensoryandmotorfibres
Duetothepresenceofmyelin
Containedwithintheventralroot
Containedwithinthedorsalroot
Locationofcellbodiesofthemotorneurons
8.TheSenses
Describethestructureandfunctionofthevertebrateeyeandtheresponseoftheeyetostimuli
Structure
Lens
Function
• Refractsandfocuseslightrays(magnification)
• Infrontofthepupil
Iris
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Controlsdiameterofthepupilandtheamountoflightenteringtheeye
Cornea
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Nobloodsupply,reliesoninterstitialfluid
Corneatransplantsareeasytoperform
Lookstransparent
Convertlighttoneuralsignalstosendtothebrainforvisualrecognition
Madeupofphotoreceptors(rods),bipolarcellsandganglioncells
Layerofbloodvesselswhichsupplyoxygenandnutrientstotheouterretina
Betweenretinaandsclera
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Toughexternalcoatthatprotectstheeyeball(whiteoftheeye)
Connectivetissue
Madeofganglionnervecells
Transfersvisualinformationfromretinatobrainviaelectricalimpulses
Providenutrientstothelensandcornea
Giveshapetotheeyeball
Maintainintraocularpressure
Refractlight
Holdlensandretinainplace
Rodsandcones
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Photo-receptors
Pupil
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Wherelightenterstheeye
Blindspot
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Smallareaoftheretinawithnovisualreceptors(norodsorcones)
Containsnervefibresthatconductimpulsestothebrainviatheopticnerve
Attacheslenstociliarymuscles
Allowslenstobulgeorflattendependingonthedesireddistance
Distantvisionàlensflattenàtensiononsuspensoryligamentsàciliarybodyrelaxes
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Containssmoothmuscle
Controlsthicknessofthelens
Ringofmusclesurroundinglens
Retina
Choroid
Sclera
Opticnerve
Aqueousand
vitreoushumour
Suspensory
ligaments
Ciliarybody
Theeyehascircumductionmovement
Photoreceptors:rodsandcones
1)Rods
• Responsibleforvisionatlow
lightlevels(scotopicvision)
• Donotmediatecolourvision
• Verysensitivebutlowresolution
• 100millionrods
• Containsproteinrhodopsin
whichismadeofopsinand
retinal(moleculederivedfrom
Vit.A)
2)Cones
• 3types:blue,green,red
• Allowsmediationofcolour
• Highresolutionbutinsensitive
tolight
• Lossofconefunctionleadstomacular
degeneration
• Foveacentraliscontainsonlyconesand
providesthesharpestvision
• 6millioncones
• Proteincalledphotopsins
Lightà electricalsignals
• Photonsabsorbedbyrodsandcones
• Phototransduction–opsinturnsthe
photonsintoelectrochemicalsignals
whicharesenttotheopticnervethen
brain
• VitaminA(coupledwithopsin)aborbsthe
lightàchangesstructureàseparates
fromopsinàelectricalsignalgeneratedto
closeupvoltagedependentchannelsà
decreasesdepolarisation
• Lateralgeniculatebody(inthethalamus)
receivessensoryinputfromtheopticnervetotheoccipitalbone
Thevisualpathway
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Opticnerveàopticchiasmaàoptictractà
superiorcolliculus(involvedinvisualreflexes)
àthalamusàoccipitallobeàvisualcortex
StructurespartofthePNS–retina,opticnerve
StructurespartoftheCNS–optictract,
colliculi,thalamus,visualcortex
Hearingdefects
Conductiondeafness–occurswhensoundwavesfail
tobeconductedfromthetympanicmembranetothe
cochlea.Canbecausedbyfluidbuild-up(replacingair),
traumaordiseasecausingfibrousscartissuein
ossicleswalls
Nervedeafness–occurswhenthecochlea,orthe
cranialnervesfromit,aredamagedtoimpulsesfailto
reachtheauditorycortexofthebrain.Suchpersonisunabletohearsound.