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Download 7. The Nervous System Identify the major structures and areas of the
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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 • Controlsdiameterofthepupilandtheamountoflightenteringtheeye Cornea • • • • • • • Nobloodsupply,reliesoninterstitialfluid Corneatransplantsareeasytoperform Lookstransparent Convertlighttoneuralsignalstosendtothebrainforvisualrecognition Madeupofphotoreceptors(rods),bipolarcellsandganglioncells Layerofbloodvesselswhichsupplyoxygenandnutrientstotheouterretina Betweenretinaandsclera • • • • • • • • • Toughexternalcoatthatprotectstheeyeball(whiteoftheeye) Connectivetissue Madeofganglionnervecells Transfersvisualinformationfromretinatobrainviaelectricalimpulses Providenutrientstothelensandcornea Giveshapetotheeyeball Maintainintraocularpressure Refractlight Holdlensandretinainplace Rodsandcones • Photo-receptors Pupil • Wherelightenterstheeye Blindspot • • • • • Smallareaoftheretinawithnovisualreceptors(norodsorcones) Containsnervefibresthatconductimpulsestothebrainviatheopticnerve Attacheslenstociliarymuscles Allowslenstobulgeorflattendependingonthedesireddistance Distantvisionàlensflattenàtensiononsuspensoryligamentsàciliarybodyrelaxes • • • 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 • • • 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.