L8_NPB_101

L8_NPB_101 - Lecture8 OnlineHandouts: Lec8Notes...

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Unformatted text preview: Lecture8 OnlineHandouts: Lec8Notes Announcements: SampleMidterm1&2 online WithoutKey Notfordiscussioninoffice hours ReviewCNS SensorySystems Somatosensory TheEar Reading(Recommended): Ch6(pg.185188) Ch6(pg.208220) REV:NervousSystemOrganizaRon 2Celltypes Neurons(funcRonal;1012) Glia(support) 2Primarydivisions Centralnervoussystem(CNS) Peripheralnervoussystem(PNS) Afferentdivision(Input) Efferentdivision(Output) REV:PercepRon ConsciousinterpretaRonofexternalworld derivedfromsensoryinput Sensoryinputdoesnotgivetruereality percepRon.Why? Humanshavereceptorsthatdetectonlyalimited numberofexisRngenergyforms Wedon'tperceiveorencodeeverything InformaRonchannelsinourbrainsarenothigh fidelityrecorders Transduc5oninnotlinear(1:1) Cerebralcortexfurthermanipulatesthedata PeripheralNervousSystem ConsistsofnervefibersthatcarryinformaRon betweentheCNSandotherpartsofthebody Afferentdivision SendsinformaRonfrominternalandexternal environmenttoCNS Visceralafferent IncomingpathwayforinformaRonfrominternalviscera(organsin bodycaviRes) SomaRc(bodysense)sensaRon SensaRonarisingfrombodysurfaceandpropriocepRon Specialsenses Vision,hearing,vesRbular,taste,smell Sensoryafferent Receptors Structuresatperipheralendingsofafferent neurons ConvertformsofsRmulusenergyintoelectrical signals(acRonpotenRals) ProcessiscalledtransducRon DetectsRmuli changedetectablebythebodyonlyifAPproduced Minimumthresholdofenergyrequired TypesofReceptorsEnergy Formofenergytransduced. PhotoreceptorsResponsivetovisiblewavelengthsoflight MechanoreceptorsSensiRvetomechanicalenergy ThermoreceptorsSensiRvetoheatandcold OsmoreceptorsDetectchangesinconcentraRonof solutesinbodyfluidsandresultantchangesinosmoRc acRvity ChemoreceptorsSensiRvetospecificchemicals IncludereceptorsforsmellandtasteandreceptorsthatdetectO2 andCO2concentraRonsinbloodandchemicalcontentofdigesRve tract NociceptorsPainreceptorsthataresensiRvetoRssue damageordistorRonofRssue TypesofReceptorsLocaRon Source/LocaRonofinformaRonsensed. Exteroreceptors Interoceptors Proprioceptors Receptors&TransducRon Receptorsmaybe: Specializedendingofanafferentneuron Separatecellcloselyassociatedwithperipheralendingofaneuron TransducRon: SRmulusaltersreceptor'spermeabilitywhichleadstogradedreceptor potenRal UsuallycausesnonselecRveopeningofallsmallcaRonchannels ThischangeinmembranepermeabilityleadstotheinfluxofNa+ions producingreceptor(generator)potenRals. ThemagnitudeofthereceptorpotenRalrepresentstheintensityof thesRmulus(thisisagradedpotenRal). AreceptorpotenRalofsufficientmagnitudecanproducea depolarizaRonofEm,leadingtoanacRonpotenRal(if>threshold). ThisacRonpotenRalispropagatedalonganafferentfibertotheCNS. ReceptorTypes&TransducRon ReceptorCell: ReceptorPoten5al ReceptorNeuron: GeneratorPoten5al AP AP Fig.63,pg.184 ReceptorAdaptaRon ReceptormembranepotenRalsreturntowards resRnglevelsbytheprocessofadaptaRon MayadaptslowlyorrapidlytosustainedsRmulaRon 2basictypesofreceptorsdefinedaccordingto theirspeedofadaptaRon Tonicreceptors Donotadaptatalloradaptslowly Musclestretchreceptors,jointproprioceptors Phasicreceptors RapidlyadapRngreceptors TacRlereceptorsinskin TonicReceptor(SteadyState) Fig.65a,pg.185 PhasicReceptor(RateofChange) Fig.65b,pg.185 Phasicvs.TonicReceptor ReceptorsareModalitySpecific Connective tissue layers Axon afferent neuron SomatosensoryTouchVibra5onMechanoreceptor Pacinian corpuscle ...
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