細胞生理6的學習資料第1頁/共71頁1.CellularmechanismofmotorcontrolThemotorneuronandmotorunitStretchreflexSectionOutline第2頁/共71頁1.1MotorneuronandmotorunitMotoneuron:αmotoneuron:Innervatesextrafusalmusclefiber.

Finalcommonpathγmotoneuron:Innervatesintrafusalmusclefiber.

Motorunit:asingleαmotoneuronandthemusclefibersitinnervates.第3頁/共71頁MotorPoolThemotorpoolisthetotalpopulationofneuronsinnervatingaparticularmuscle.第4頁/共71頁SizePrincipleWhenacontractionoccurs,smallmotorunitsfirefirst,asthestrengthofcontractionincreases,largerunitsarerecruited,theorderlyrecruitmentofmotoneuronsisreferredtoassizeprinciple

第5頁/共71頁1.2StretchreflexStretchreflex:Stretchingorelongatingamusclecausesittocontractwithinashorttimeperiod.TendonreflexMuscletonus第6頁/共71頁TendonreflexAphasicpart,exemplifiedbytendonjerksSensor:musclespindleMonosynapticreflex第7頁/共71頁MuscletoneAtonicpartSensor:musclespindleMultisynapticreflexImportantformaintainingposture第8頁/共71頁NuclearbagfiberandnuclearchainfiberNuclearbagfiber:dynamicresponseNuclearchainfiber:staticresponse第9頁/共71頁Dynamicresponseandstaticresponse第10頁/共71頁Roleof-motoneuronsStimulationof-efferentcausesthecontractileendsofintrafusalfibertoshorten,stretchesNBF/NCF,initiatingimpulsesinIaafferents,thisinturnleadstoexcitationof-neurons.Increased-efferentdischargeincreasesspindlesensitivity.第11頁/共71頁InversestretchreflexInversestretchreflex:Theactivecontractionofamusclealsocausesreflexinhibitionofthecontraction.Thisresponseiscalledtheinversemyotaticreflex.第12頁/共71頁InversestretchreflexSensor:GolgitendonorganAfferentfiber:IbInhibitoryinterneuron第13頁/共71頁ReviewCellularmechanismofmotorcontrolMotorneurons:αγ

MotorunitMotorpoolSizeprincipleStretchreflex:tendonreflex,muscletonusMusclespindle:nuclearbag,nuclearchainInversestretchreflex:tendonorgan第14頁/共71頁2.ControlofmovementatthespinalcordlevelSpinalshock:Inallvertebrates,transectionofthespinalcordisfollowedbyaperiodofspinalshockduringwhichallspinalreflexresponsesareprofoundlydepressed.第15頁/共71頁MechanismofspinalshockTheinitialshockisconsideredtobeduetothesuddenwithdrawaloftonicfacilitatoryinfluencefromthebrain第16頁/共71頁Flexion-withdrawalreflexCrossed-extensionreflexPostureregulatingmechanismsatthespinalcordlevel第17頁/共71頁Flexion-withdrawalreflexFlexion-withdrawalreflex:Thelimbisquicklywithdrawnfromapainfulstimulus,usuallybysimultaneouscontractionofalltheflexormusclesinthelimb第18頁/共71頁PolysynapticreflexConsistsofacontractionofflexorsandarelaxationofextensorsinthestimulatedlimbProtectivereflexFlexion-withdrawalreflex第19頁/共71頁Crossed-extensionreflex:Anoppositeeffectinthecontralaterallimb,thatis,excitationofextensormotorneuronsandinhibitionofflexormotorneuronsCrossed-extensionreflex第20頁/共71頁3.PosturecontrolbythebrainstemMechanismofdecerebraterigidityFacilitatoryandinhibitoryareaofmuscletonusα-rigidityandγ-rigidity

SectionOutline第21頁/共71頁3.2PosturereflexpathwaysLateralmotorpathways:voluntarymovementMediatemotorpathways:posturereflexVestibulospinaltractsReticulospinaltractsMedialLateral第22頁/共71頁4.Corticalcontrolofvoluntarymovement第23頁/共71頁4.CorticalcontrolofvoluntarymovementCorticalmotorareaPrimarymotorcortexSecondarymotorcortexLateralmotorpathwaysCorticospinaltractCorticobulbartractRubrospinaltractSectionOutline第24頁/共71頁4.1CorticalmotorareaBrodmann4area:Primarymotorcortex,MI

ExecutionofmovementBrodmann6area:Secondarymotorcortex,MIIPlanningmovementSupplementarymotorarea,SMAComplexmotorsequencePremotorarea,PMTargetedmovement

第25頁/共71頁4.1CorticalmotorareaBrodmann4area:Primarymotorcortex,MIExecutionofmovementBrodmann6area:Secondarymotorcortex,MII

PlanningmovementSupplementarymotorarea,SMA

ComplexmotorsequencePremotorarea,PM

Targetedmovement

第26頁/共71頁4.2LateralmotorpathwaysCorticospinaltractLateralcorticospinaltractAnteriorcorticospinaltractCorticobulbartractRubrospinaltract第27頁/共71頁5.FunctionofthebasalgangliaFunctionalcircuitryofthebasalgangliaDirectpathwaysIndirectpathwaysDopaminemodulationDiseasesofthebasalgangliaParkinson’sdiseaseHuntington’sdiseaseOutline第28頁/共71頁5.1FunctionalcircuitryofthebasalgangliaNeostriatumGlobuspallidusSubtantianigraSubthalamicnucleusCaudatenucleusPutamanExternalglobuspallidusInternalglobuspallidusSubstantianigraparsreticulataSubstantianigraparscompacta第29頁/共71頁Basalganglia第30頁/共71頁DirectpathwayIncreasetheexcitabilityofcortexIndirectpathwayDecreasetheexcitabilityofcortexDirectpathwayIndirectpathwayBasalgangliacircuitD1D2第31頁/共71頁Parkinson’sdiseaseHuntington’sdiseaseBasalgangliadisorders第32頁/共71頁JamesParkinson,1917

“...involuntarytremulousmotion,withlessenedmuscularpower,inpartsnotinactionandevenwhensupported;withapropensitytobendthetrunkforwards,andtopassfromawalkingtoafunningpace,thesensesandtheintellectsuninjured.”

?rhythmictremoratrest

?rigiditywith“cog-wheelcharacteristic”

?akinesiaClinicalCharacteristics第33頁/共71頁NeuralmechanismofparkinsonismNormalParkinson’sdisease(PD)第34頁/共71頁Pathology

ofParkinson’sdiseaseLossofdopaminergicneuronsinthesubstantianigraleadtodecreasedactivityinthedirectpathwayandincreasedactivityintheindirectpathway.Asaresult,thalamicinputtothemotorareaofthecortexisreducedandthepatientexhibitsrigidityandbradykinesia.第35頁/共71頁L-dopaL-dopatakenupbydopaminergicneuronsinthesubstantianigraandconvertedtodopaminebyL-AminoAcidDecarboxylase(LAAD)Asthediseaseprogresses,moredopaminergicneuronsarelostandtheeffectivenessofL-dopaasareplacementtherapydeclines.第36頁/共71頁Huntington’schoreaOnset:30-45yearsExcessivemovementsRapid,jerky,involuntaryMildtwitchinglarger,moregeneralizedProgressivedementiaOthercharacteristicsGrimaceDancinggaitHuntington’sdisease第37頁/共71頁Huntington’sdiseaseNormalHuntington’sdisease(HD)第38頁/共71頁Cause&TreatmentofHDGenetic:autosomaldominantAbnormalproteinbuildsup&killsbraincellsespeciallyinbasalgangliaandcortexSurgery第39頁/共71頁SurgeryforHuntington’sdiseaseHuntington’sdisease(HD)第40頁/共71頁6.CerebellarfunctionFunctionaldivisionsVestibulocerebellumSpinocerebellumCerebrocerebellumCytoarchitectureofthecerebellarcortexOutline第41頁/共71頁Functionaldivisions第42頁/共71頁Vestibulocerebellum:TheoldestpartofthecerebellumReceivesinputfromthevestibularsystemOutputgoestothevestibularnucleiFunctionstocontrolequilibriumandeyemovementsFunctionaldivisions第43頁/共71頁Spinocerebellum:ConsistsofvermisandintermediatezonesReceivesproprioceptiveinputfromthebodyaswellasacopyofthe“motorplan”fromthemotorcortexBycomparingplanwithperformance,itsmoothesandcoordinatesmovementsthatareongoingFunctionaldivisions第44頁/共71頁Cerebrocerebellum

OccupiesthelateralaspectsofthecerebellarhemispheresInputcomesfromthecerebralcortexOutputisdirectedtothedentatenucleiInteractwiththemotorcortexinplanningandprogrammingmovementsFunctionaldivisions第45頁/共71頁PurkinjecellGranulecellBasketcellStellatecellGolgicellThecerebellarcortexisorganizedintothreelayersandcontainsfivetypesofneurons第46頁/共71頁PurkinjecellThebiggestneuronsGABAergicExtensivedendriticarborsthatextendthroughoutthemolecularlayerReceiveinputfromtheparallelfibersTheonlyoutputfromthecerebellum

Thecerebellarcortexisorganizedintothreelayersandcontainsfivetypesofneurons第47頁/共71頁GranulecellsReceiveinputformthemossyfibersInnervatePurkinjecellsSendanaxontothemolecularlayer,theyarecalledparallelfibersThecerebellarcortexisorganizedintothreelayersandcontainsfivetypesofneurons第48頁/共71頁BasketcellsLocatedinthemolecularlayerReceiveinputfromtheparallelfibersTheaxonsfromabasketaroundthecellbodyandaxonhillockofPurkinjecelltheyinnervateThecerebellarcortexisorganizedintothreelayersandcontainsfivetypesofneurons第49頁/共71頁StellatecellsLocatedinthemolecularlayerbutmoresuperficialGolgicellsLocatedingranularlayerAxonsprojecttothedendritesofthegranulecellThecerebellarcortexisorganizedintothreelayersandcontainsfivetypesofneurons第50頁/共71頁BothareexcitatoryClimbingfibersMossyfibersMaininputstothecerebellarcortex第51頁/共71頁Climbingfibers

Comeformasinglesource,theinferiorolivarynucleiProjecttotheprimarydendritesofPurkinjecell,aroundwhichitentwineslikeaclimbingplant第52頁/共71頁Mossyfibers

ProvidedirectproprioceptiveinputfromallpartsofthebodyplusinputfromthecerebralcortexTheyendonthedendritesofgranulecellsincomplexsynapticgroupingscalledglomeruli第53頁/共71頁SummaryCellularmechanismofmotorcontrolMotorneurons:αγ

MotorunitMotorpoolSizeprincipleStretchreflex:tendonreflex,muscletonusMusclespindle:nuclearbag,nuclearchainInversestretchreflex:tendonorgan第54頁/共71頁ControlofmovementatthespinalcordSpinalshockFlexorwithdrawalreflexCrossedextensionreflexPosturecontrolbythebrainstemDecerebraterigidityCorticalcontrolvoluntarymovementSummary第55頁/共71頁ControlofmovementinthebasalgangliaDirectpathwayIndirectpathwayParkinson’sdiseaseHuntington’sdiseaseControlmovementinthecerebellumFunctionaldivisionFivetypesofneuronsTwomaininputstothecerebellumSummary第56頁/共71頁第57頁/共71頁1.1MotorneuronandmotorunitMotoneuronαmotoneuron:Innervatesextrafusalmusclefiber.

Finalcommonpath.γmotoneuron:Innervatesintrafusalmusclefiber.

βmotoneuron:InnervatesbothMotorunit:asinglemotoneuronandthemusclefibersitinnervates.第58頁/共71頁MotorPool&RecruitmentThemotorpoolisthetotalpopulationofneuronsinnervatingaparticularmuscle,e.g.,25,000musclefibersincatsoleusaresuppliedby100-motoneurons,singlecontractionofwholemusclecanbegradedin100stepsbyrecruitmentofmotorunits.第59頁/共71頁3.1MechanismofdecerebraterigidityDecerebraterigidity:Inexperimentalanimalsinwhichthehindbrainandspinalcordareisolatedfromtherestofbrainbytransectionofthebrainstematthesuperiorborderofthepons,themostprominentfindingismarkedspasticityofthebodymusculature.Theresultingpatternofspasticityiscalled第60頁/共71頁MechanismofdecerebraterigidityDecerebraterigidity:isfoundtobespasticityduetodiffusefacilitationofstretchreflexes.ThefacilitationisduetotwofactorsIncreasedgeneralexcitabilityofthemotorneuronpoolIncreaseintherateofdischargeintheγ-efferentneurons.第61頁/共71頁DecorticaterigidityThemorecommonpatternofextensorrigidityinthelegsandmoderateflexioninthearmsisactuallydecorticaterigidityduetolesionsofthecerebralcortex,withmostofthebrainstemintact.第62頁/共71頁3.3PosturecontrolbythebrainstemAttitudinalreflexToniclabyrinthinereflexTonicneckreflexRightingreflex第63頁/共71頁MotorUnitThenumberofmusclefibersinamotorunitrangesfromafew,muscleofeyeforfinecontrol,tothousandsofmusclefibers,largeproximalmuscleoflimbs.Smoothnessandprecisionofmovementarebroughtaboutbyvaryingthenumberandtimingofmotorunitbroughtintoplay.第64頁/共