2023学年完整公开课版Lecture6Sensorysystems

Lecture6:

Sensory&MotorSystemsSensorySystemsVisionHearingTasteSmellEquilibriumSomaticSensesSensorySystemsSomaticsensoryGeneral–transmitimpulsesfromskin,skeletalmuscles,andjointsSpecialsenses-hearing,balance,visionVisceralsensoryTransmitimpulsesfromvisceralorgansSpecialsenses-olfaction(smell),gustation(taste)SensorySystemsPropertiesofSensorySystemsStimulus-energysourceInternalvs.ExternalReceptorsSenseorgans-specializedtorespondtostimuliTransducers-stimulusenergyconvertedintoactionpotentialsConductionAfferentpathwayNerveimpulsestotheCNSTranslationCNSintegrationandinformationprocessingSensationandperception–yourrealitySensoryPathwaysStimulusasphysicalenergysensoryreceptoractsasatransducerStimulus>thresholdactionpotentialtoCNSIntegrationinCNScerebralcortexoractedonsubconsciouslyClassificationbyFunction(Stimuli)Mechanoreceptors–respondtotouch,pressure,vibration,stretch,anditchThermoreceptors–sensitivetochangesintemperaturePhotoreceptors–respondtolightenergy(e.g.,retina)Chemoreceptors–respondtochemicals(e.g.,smell,taste,changesinbloodchemistry)Nociceptors–sensitivetopain-causingstimuliOsmoreceptors–detectchangesinconcentrationofsolutes,osmoticactivityBaroreceptors–detectchangesinfluidpressureClassificationbyLocationExteroceptors–sensitivetostimuliarisingfromoutsidethebodyLocatedatornearbodysurfacesIncludereceptorsfortouch,pressure,pain,andtemperatureInteroceptors–(visceroceptors)receivestimulifrominternalvisceraMonitoravarietyofstimuliProprioceptors–monitordegreeofstretchLocatedinmusculoskeletalorgansClassificationbyLocationClassificationbyStructureSomaticSensesGeneralsomatic–includetouch,pain,vibration,pressure,temperatureProprioceptive–detectstretchintendonsandmuscleprovideinformationonbodyposition,orientationandmovementofbodyinspaceSomaticReceptorsDividedintotwogroupsFreeorUnencapsulatednerveendingsEncapsulatednerveendings-consistofoneormoreneuralendfibersenclosedinconnectivetissueFreeNerveEndingsAbundantinepitheliaandunderlyingconnectivetissueNociceptors-respondtopainThermoreceptors-respondtotemperatureEncapsulatedNerveEndings-ProprioceptorsSpecialSensesTaste,smell,sight,hearing,andbalanceLocalized–confinedtotheheadregionReceptorsarenotfreeendingsofsensoryneuronsbutspecializedreceptorcellsFigure10-4:SensorypathwaysTheEar:HearingandEquilibriumTheear–receptororganforhearingandequilibriumComposedofthreemainregionsOuterear–functionsinhearingMiddleear–functionsinhearingInnerear–functionsinbothhearingandequilibriumTheOuter(External)EarAuricle(pinna)-helpsdirectsoundsExternalacousticmeatusLinedwithskinContainshairs,sebaceousglands,andceruminousglandsTympanicmembraneFormstheboundarybetweentheexternalandmiddleearTheMiddleEarThetympaniccavityAsmall,air-filledspaceLocatedwithinthepetrousportionofthetemporalboneMedialwallispenetratedbyOvalwindowRoundwindowPharyngotympanictube(auditoryoreustachiantube)-LinksthemiddleearandpharynxFigure16.17TheMiddleEarEarossicles–smallestbonesinthebodyMalleus–attachestotheeardrumIncus–betweenthemalleusandstapesStapes–vibratesagainsttheovalwindowTheInner(Internal)EarInnerear–alsocalledthelabyrinthBonylabyrinth–acavityconsistingofthreepartsSemicircularcanalsVestibuleCochleaBonylabyrinthisfilledwithperilymphTheMembranousLabyrinthMembranouslabyrinth-seriesofmembrane-walledsacsandductsFitwithinthebonylabyrinthConsistsofthreemainpartsSemicircularductsUtricleandsacculeCochlearductFilledwithaclearfluid–endolymphFigure16.18TheCochleaAspiralingchamberinthebonylabyrinthCoilsaroundapillarofbone–themodiolusSpirallamina–aspiralofboneinthemodiolusThecochlearnerverunsthroughthecoreofthemodiolusTheCochleaThecochlearduct(scalamedia)–containsreceptorsforhearingLiesbetweentwochambersThescalavestibuliThescalatympaniThevestibularmembrane–theroofofthecochlearductThebasilarmembrane–thefloorofthecochlearductTheCochleaThecochlearduct(scalamedia)–containsreceptorsforhearingOrganofCorti–thereceptorepitheliumforhearingConsistsofhaircells(receptorcells)TheRoleoftheCochleainHearingFigure16.20AuditoryPathwayfromtheOrganofCortiTheascendingauditorypathwayTransmitsinformationfromcochlearreceptorstothecerebralcortexFigure16.23TheVestibuleUtricleandsaccule–suspendedinperilymphTwoegg-shapedpartsofthemembranouslabyrinthHousethemacula–aspotofsensoryepitheliumMacula–containsreceptorcellsMonitorthepositionoftheheadwhentheheadisstillContainscolumnarsupportingcellsReceptorcells–calledhaircellsSynapsewiththevestibularnerveTheVestibuleFunctionoftheMaculaeFigure16.21bTheSemicircularCanalsLieposteriorandlateraltothevestibuleAnteriorandposteriorsemicircularcanalslieintheverticalplaneatrightanglesLateralsemicircularcanalliesinthehorizontalplaneTheSemicircularCanalsSemicircularduct–snakesthrougheachsemicircularcanalMembranousampulla–locatedwithinbonyampullaHousesastructurecalledacristaampullaris

CristaecontainreceptorcellsofrotationalaccelerationEpitheliumcontainssupportingcellsandreceptorhaircellsStructureandFunctionoftheCristaAmpullarisFigure16.22bTheChemicalSenses:TasteandSmellTaste–gustationSmell–olfactionReceptors–classifiedaschemoreceptors

RespondtochemicalsTaste–GustationTastereceptorsOccurintastebudsMostarefoundonthesurfaceofthetongueLocatedwithintonguepapillaeTwotypesofpapillae(withtastebuds)FungiformpapillaeCircumvallatepapillaeTasteBudsCollectionof50–100epithelialcellsContainthreemajorcelltypes(similarinallspecialsenses)SupportingcellsGustatorycellsBasalcellsContainlongmicrovilli–extendthroughatasteporeTasteSensationandtheGustatoryPathwayFourbasicqualitiesoftasteSweet,sour,salty,andbitterAfifthtaste–umami,“deliciousness”

NostructuraldifferenceamongtastebudsGustatoryPathwayfromTasteBudsTasteinformationreachesthecerebralcortexPrimarilythroughthefacial(VII)andglossopharyngeal(IX)nervesSometasteinformationthroughthevagusnerve(X)SensoryneuronssynapseinthemedullaLocatedinthesolitarynucleusFigure16.2Smell(Olfaction)Olfactoryepitheliumwitholfactoryreceptors,supportingcells,basalcellsOlfactoryreceptorsaremodifiedneuronsSurfacesarecoatedwithsecretionsfromolfactoryglandsOlfactoryreceptioninvolvesdetectingdissolvedchemicalsastheyinteractwithodorantbindingproteinsOlfactoryReceptorsBipolarsensoryneuronslocatedwithinolfactoryepitheliumDendriteprojectsintonasalcavity,terminatesinciliaAxonprojectsdirectlyupintoolfactorybulbofcerebrumOlfactorybulbprojectstoolfactorycortex,hippocampus,andamygdaloidnucleiMotorSystemsWhyistheMotorSystemImportant?Allobservablebehaviorisdirectlyrelatedtoactivityinthemotorsystem.Withoutthemotorsystem,wecouldexperiencesensation,think,reason,problemsolve,read,write,anddomentalmath,butwewouldnotbeabletocommunicateourthoughtsandabilitiestoanyone.BasisofMusclesSkeletalMuscles(vs.smoothmusclesorcardiacmuscle) -striated(striped)appearancebecausetheyarecomprisedofmusclefibers -movethroughapullaction(contraction) -workinpairswithareciprocalmuscle (bicepcontractsandtricepsrelaxes) -stimulatedbyaMotorNeuron

AnatomyoftheMuscle

Striatedmusclesaremadeofmusclefibersthathavetwoparts,outerandinner:Outerfiber=extrafusalfiberInnerfiber=intrafusalfiber

Wrappedaroundtheintrafusalfiberisasensorynervethatpicksupthesensationofstretch.Thisrepresentsonlyonemusclefiber-amusclehasmanyfibersOuterfiber=extrafusalfiberInnerfiber=intrafusalfiber

Eachmusclefiberhasagammamotorneuronthatsynapsesontheintrafusalfiber.Thealphamotorneuronsynapsesontheextrafusalfibers.Onealphamotorneuroncanstimulatenumerousfibers.Thisiscalledthemotorunit.Theneurallinkbetweenthealphamotorneuronandthemusclefiberiscalledtheneuromuscularjunction.Alphamotor

neuronGammaMotorNeuronDorsalhornforsensoryinputVentralhornformotoroutputTheratiobetweenthealphamotorneuronandthenumberofmusclesfibersitinnervatesisassociatedwiththedegreeofdexterityneededinthemovementhighratio(1:150)=contractionoflargemuscleslowratio(1:10)=contractionofsmallmusclesneededforfinemovementsMotorHomunculusisrelatedtothenumberofalphamotorneuronsneededtoinnervatemusclesofvariousregionsofourbody.ComparingtheAnatomyoftheCNS&NeuromuscularJunctionMotorUnitAlphaMotorNeuronMuscleFiberEndplateNTisAcetylcholineNicotinicReceptorsCalciumentersEndplatePotential(EPP)MuscleContractionorMuscleActionPotential&movementCNSSynapsePresynapticNeuronPostsynapticNeuronDendriteManydifferentNTsManydifferentreceptorsSodiumentersEPSPActionPotential&releaseofNT========Howislimbpositionmaintained?Involuntarymovement(i.e.posture):continualcontractionandrelaxationofthemusclesinourfeetandcalves.Voluntarymovement:Stretchoftheintrafusalfibercausescontractionoftheextrafusalfiberviaalphamotorneuron.Keepingthemovementatthispositionrequiresadirectsignalfromthebrain.MuscleInnervationMusclesworkinpairsandopposeseachother.Thisisreferredtoasreciprocalinnervation.Whatifbothmusclescontractedatthesametime?

Theneuralmechanismofreciprocalinnervationisabittricky…CommonMovementPathwayAlphaMotorNeuronistheFinalCommonPathforallmovement.Movementcanbegeneratedfrom: -sensorysignalsinthemusclespindlelikethestretchreflex -sensorysignalsfromskinasinthepainwithdrawalresponse -involuntarysignalsfromthebrainstemforposture,keepingusuprightwithoutconsciousattention -signalsfromthebrainforvoluntarymovement

Excitation-ContractionCouplingMusclecontractionAlphamotorneuronsreleaseAchAChproduceslargeEPSPinmusclefibers(vianicotinicAchreceptorsEPSPevokesactionpotentialActionpotential(excitation)triggersCa2+release,leadstofibercontractionRelaxation,Ca2+levelsloweredbyorganellereuptakeExcitation-ContractionCouplingExcitation-ContractionCouplingVoluntaryMovement:InstructionsfromCerebralCortexDorsolateralPrefrontalCortex:directsmovementofourlimbs(asinreaching)andmovementsofourfingers.Actualsignalformovementmustgothrou