離子通道和神經(jīng)元的電活動(dòng)Neuronal-Electric-Activities課件

NeuronalElectricActivities

神經(jīng)元的電活動(dòng)主講教師劉風(fēng)雨萬(wàn)有神經(jīng)科學(xué)研究所、神經(jīng)生物學(xué)系NeuronalElectricActivities

神NeuronalElectricActivitiesInclude:RestPotential

(Chapter3)ActionPotential(Chapter4)LocalPotentialsPost-SynapticPotentialExcitatoryPost-SynapticPotentialInhibitoryPost-SynapticPotentialEnd-platePotentialReceptorPotentialNeuronalElectricActivitiesIChapter3

TheNeuronalMembraneatRestTheCASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTheMOVEMENTOFIONSDiffusionElectricityTheIONICBASISOFRESTINGMEMBRANEPOTENTIALEquilibriumPotentialTheDistributionofIonsAcrosstheMembraneRelativeIonPermeabilitiesofMembraneatRestTheImportanceofRegulatingtheExternalPotassiumConcentrationCONCLUDINGREMARKSChapter3

TheNeuronalMembranCytosolandExtracellularFluidWater:Itsunevendistributionofelectricalcharge,soH2OisapolarmoleculeIons:SaltdissolvesreadilyinwaterbecausethechargedportionsofthewatermoleculehaveastrongerattractionfortheionsthantheyhaveforeachotherCytosolandExtracellularFluiThePhospholipidMembrane(磷脂膜)Thelipidsoftheneuronalmembraneforming:abarriertowater-solubleionsabarriertowater頭端-極性磷酸鹽-親水尾端-非極性碳?xì)浠衔?疏水5ThePhospholipidMembrane(磷脂膜ProteinTheseproteinsprovideroutesforionstocrosstheneuronalmembrane.Therestingandactionpotentialsdependonspecialproteinsthatspanthephospholipidbilayer.ProteinTheseproteinsprovideProtein–AminoAcidsProtein–AminoAcidsThePeptideBond(肽鍵)and

aPolypeptide(多肽)ThePeptideBond(肽鍵)and

aPFigure3.6ProteinStructureTheprimarystructureThesecondarystructureThetertiarystructureThequaternarystructureEachofthedifferentpolypeptidescontributingtoaproteinwithquaternarystructureiscalledasubunit(亞基).Figure3.6ProteinStructureThChannelProteinsChannelproteinissuspendedinaphospholipidbilayer,withitshydrophobic

(疏水的)portioninsidethemembranehydrophilic

(親水的)endsexposedtothewateryenvironmentsoneithersideFigure3.7AMembraneIonChannel10ChannelProteinsChannelproteiTwoPropertiesofIonChannelsIonselectivity(離子選擇性)ThediameteroftheporeThenatureoftheRgroupsliningitGating(門控特性)Channelswiththispropertycanbeopenedandclosed-gatedbychangesinthelocalmicroenvironmentofthemembraneTwoPropertiesofIonChannelsIonPumps(離子泵)IonpumpsareenzymesthatusetheenergyreleasedbythebreakdownofATPtotransportcertainionsacrossthemembraneIonPumps(離子泵)IonpumpsareeChapter3

TheNeuronalMembraneatRestTHECASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTHEMOVEMENTOFIONSDiffusionElectricityTHEIONICBASISOFRESTINGMEMBRANEPOTENTIALEquilibriumPotentialTheDistributionofIonsAcrosstheMembraneRelativeIonPermeabilitiesofMembraneatRestTheImportanceofRegulatingtheExternalPotassiumConcentrationCONCLUDINGREMARKSChapter3

TheNeuronalMembranTHEMOVEMENTOFIONSAchannelacrossamembraneislikeabridgeacrossariver.AnopenchannelAnetmovementofionsacrossthemembrane.Ionmovementrequiresthatexternalforcesbeappliedtodriveionsacross.Twofactorsinfluenceionmovementthroughchannels:Diffusion(擴(kuò)散)Electricity

(電勢(shì)差)THEMOVEMENTOFIONSAchannelDiffusionTemperature-dependentrandommovementofionsandmoleculestendstodistributetheionsevenlythroughoutthesolutionsothatthereisanetmovementofionsfromregionsofhighconcentrationtoregionsoflowconcentration.Thismovementiscalleddiffusion

(擴(kuò)散).Adifferenceinconcentrationiscalledaconcentrationgradient

(濃度梯度).15DiffusionTemperature-dependentFigure3.8DiffusionDrivingionsacrossthemembranebydiffusionhappenswhenThemembranepossesseschannelspermeabletotheionsThereisaconcentrationgradientacrossthemembraneFigure3.8DiffusionDrivingioElectricityAnotherwaytoinduceanetmovementofionsinasolutionistouseanelectricalfield(電場(chǎng)),becauseionsareelectricallychargedparticles.Oppositechargesattractandlikechargesrepel.ElectricityAnotherwaytoinduFigure3.9

ThemovementofionsinfluencedbyanelectricalfieldOppositechargesattractandlikechargesrepelFigure3.9

ThemovementofioElectricityTwoimportantfactorsdeterminehowmuchcurrent(I)willflow:Electricalpotential(V,電勢(shì))Electricalconductance(g,電導(dǎo))Electricalconductance

Electricalresistance(電阻,R=1/g)Ohm’slaw:I=gVElectricityTwoimportantfactoFigure3.10ElectricalcurrentflowacrossamembraneDrivinganionacrossthemembraneelectricallyrequiresThemembranepossesseschannelspermeabletotheionsThereisaelectricalpotentialdifferenceacrossthemembrane20Figure3.10ElectricalcurrentDiffusionandElectricityElectricalchargedionsinsolutiononeithersideoftheneuronalmembrane.(帶電離子溶解在細(xì)胞膜兩側(cè)的溶液中)Ionscancrossthemembraneonlybyproteinchannel.(離子必須通過(guò)離子通道實(shí)現(xiàn)跨膜運(yùn)動(dòng))Theproteinchannelscanbehighlyselectiveforspecificions.(離子通道對(duì)離子具有高度的選擇性)Themovementofanyionthroughchanneldependsontheconcentrationgradientandthedifferenceinelectricalpotential

acrossthemembrane.(離子的跨膜運(yùn)動(dòng)依賴于膜兩側(cè)的濃度梯度和電位差)DiffusionandElectricityElectChapter3

TheNeuronalMembraneatRestTheCASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTheMOVEMENTOFIONSDiffusionElectricityTheIONICBASISOFRESTINGMEMBRANEPOTENTIALEquilibriumPotentialTheDistributionofIonsAcrosstheMembraneRelativeIonPermeabilitiesofMembraneatRestTheImportanceofRegulatingtheExternalPotassiumConcentrationCONCLUDINGREMARKSChapter3

TheNeuronalMembranThemembranepotential(膜電位)isthevoltageacrosstheneuronalmembraneatanymoment,representedbythesymbolmV.Microelectrode(微電極)andmVmeasurementTHEIONICBASISOFTHERESTINGMEMBRANEPOTENTIAL(靜息電位)Themembranepotential(膜電位)iEstablishingEquilibriumPotential(平衡電位)Figure3.12EstablishingequilibriuminaselectivelypermeablemembraneNopotentialdifferenceVm=0mVThediffusionalforce=TheelectricalforceVm=-80mV20:1EstablishingEquilibriumPotenEquilibriumpotentialsTheelectricalpotentialdifferencethatexactlybalancesanionicconcentrationgradientiscalledanionicequilibriumpotential,orsimplyequilibriumpotential

(當(dāng)離子移動(dòng)所產(chǎn)生的電位差和離子移動(dòng)所造成的濃度勢(shì)能差平衡時(shí)，不再有離子的凈移動(dòng)，這時(shí)膜兩側(cè)的電位差稱為離子的平衡電位)Generatingasteadyelectricalpotentialdifferenceacrossamembranerequires

Anionicconcentrationgradient

Selectiveionicpermeability25EquilibriumpotentialsTheelecBeforemovingontothesituationinrealneurons,fourimportantpointsshouldbemade:Largechangesinmembranepotentialarecausedbyminusculechangesinionicconcentrations(僅需要微小的離子濃度改變就可以引起膜電位大幅度的變化)100mM99.99999mMVm=-80mVVm=0mVBeforemovingontothesituatBeforemovingontothesituationinrealneurons,fourimportantpointsshouldbemade:2.Thenetdifferenceinelectricalchargeoccursattheinsideandoutsidesurfacesofthemembrane(膜內(nèi)外兩側(cè)電荷的不同僅僅分布于膜的內(nèi)外側(cè)面，而不是分布于整個(gè)細(xì)胞的內(nèi)外液)Figure3.13(5nm)BeforemovingontothesituatBeforemovingontothesituationinrealneurons,fourimportantpointsshouldbemade:Ionsaredrivenacrossthemembraneatarateproportionaltothedifferencebetweenthemembranepotentialandtheequilibriumpotential(離子的跨膜速率與膜電位和平衡電位的差值成正比).NetmovementofK+occursasthemembranepotentialdifferedfromtheequilibriumpotential.Thisdifference(Vm-Eion)iscalledtheionicdrivingforce(離子驅(qū)動(dòng)力).Iftheconcentrationdifferenceacrossthemembraneisknownforanion,anequilibriumpotentialcanbecalculatedforthation(根據(jù)某離子膜兩側(cè)濃度的差值可以計(jì)算該離子的平衡電位).BeforemovingontothesituatNa+EquilibriumPotentialFigure3.14AnotherexampleestablishingequilibriuminaselectivelypermeablemembraneNa+EquilibriumPotentialFiguTheNernstEquationTheexactvalueofanequilibriumpotentialinmVcanbecalculatedusingtheNernstequation,whichtakesintoconsideration:ThechargeoftheionThetemperatureTheratiooftheexternalandinternalionconcentrationsPage64.Box3.2.MarkF.Bear,etal.ed.Neuroscience:ExploringtheBrain.2ndedition.EK=2.303log

30TheNernstEquationTheexactvFigure3.15Figure3.15Approximateionconcentrationsoneithersideofaneuronalmembrane.Figure3.15Figure3.15RelativeIonPermeabilitiesofMembraneatRestTherestingmembranepermeabilityisfortytimesgreatertoK+thantoNa+Therestingmembranepotentialis–65mVRelativeIonPermeabilitiesofTheDistributionofIonsAcrosstheMembraneIonicconcentrationgradientsareestablishedbytheactionsofionspumpsintheneuronalmembrane(膜內(nèi)外兩側(cè)的離子濃度梯度的形成依賴于離子泵的活動(dòng))Twoimportantionpumps:Thesodium-potassiumpump(鈉鉀泵)isanenzymethatbreaksdownATPinthepresenceofinternalNa+.Thecalciumpump(鈣泵)isanenzymethatactivelytransportsCa2+outofthecytosolacrossthecellmembrane.TheDistributionofIonsAcrosFigure3.16Figure3.16Thesodium-potassiumpump.K+K+Na+Na+Figure3.16Figure3.16ThesoFigure4.4Membranecurrentsandconductances35Figure4.4MembranecurrentsanThemostpotassiumchannelshavefoursubunitsthatarearrangedlikethestavesofabarreltoformaporeOfparticularinterestisaregioncalledtheporeloop(孔袢),whichcontributestotheselectivityfilterthatmakesthechannelpermeablemostlytoK+ions.ThewideworldofpotassiumchannelsThemostpotassiumchannelshaFigure3.18Figure3.18AviewoftheatomicstructureofthepotassiumchannelporeFigure3.18Figure3.18TheimportanceofregulatingtheexternalpotassiumconcentrationIncreasingextracellularpotassiumdepolarizesneuronsFigure3.19Thedependenceofmembranepotentialonexternalpotassiumconcentration.550-65-17TheimportanceofregulatingtTwoprotectivemechanismsinthebrainBlood-brainbarrier(血腦屏障)limitsthemovementofpotassium(andotherblood-bornesubstances)intotheextracellularfluidofthebrainGlia,particularlyastrocytes,takeupextracellularK+wheneverconcentrationsrise,astheynormallydoduringperiodsofneuralactivity.TwoprotectivemechanismsintFigure3.20Figure3.20Potassiumspatialbufferingbyastrocytes.Whenbrain[K+]oincreasesasaresultoflocalneuralactivity,K+entersastrocytesviamembranechannels.TheextensivenetworkofastrocyticprocesseshelpsdissipatetheK+overalargearea.40Figure3.20Figure3.2040Chapter3

TheNeuronalMembraneatRestTheCASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTheMOVEMENTOFIONSDiffusionElectricityTheIONICBASISOFRESTINGMEMBRANEPOTENTIALEquilibriumPotentialTheDistributionofIonsAcrosstheMembraneRelativeIonPermeabilitiesofMembraneatRestTheImportanceofRegulatingtheExternalPotassiumConcentrationCONCLUDINGREMARKSChapter3

TheNeuronalMembranNeuronalElectricActivitiesInclude:RestPotential(Chapter3)ActionPotential(Chapter4)LocalPotentialsPost-SynapticPotentialExcitatoryPost-SynapticPotentialInhibitoryPost-SynapticPotentialEnd-platePotentialReceptorPotentialNeuronalElectricActivitiesIChapter4TheActionPotentialPROPERTIESOFTHEACTIONPOTENTIALTheUpsandDownsofanActionPotentialsGenerationofanActionPotentialTheGenerationofMultipleActionPotentialsTHEACTIONPOTENTIALINTHEORYMembraneCurrentsandConductancesTheInsandOutsofActionPotentialTHEACTIONPOTENTIALINREALITYTheVoltage-GatedSodiumChannelVoltage-GatedPotassiumChannelsPuttingthePiecesTogetherACTIONPOTENTIALCONDUCTIONFactorinfluencingconductionvelocityACTIONPOTENTIALS,AXONS,ANDDENDRITESCONCLUDINGREMARKSChapter4TheActionPotentiaMethodsofRecordingActionPotentials細(xì)胞內(nèi)記錄細(xì)胞外記錄示波器MethodsofRecordingActionPoTheUpsandDownsofanActionPotentials上升支（去極化）下降支（復(fù)極化）超射超極化激活后電位2ms-65mV45TheUpsandDownsofanActionGenerationofanactionpotentialTheperceptionofsharppainwhenathumbtackentersyourfootiscausedbythegenerationofactionpotentialsincertainnervefibersintheskin:Thethumbtackenterstheskin(圖釘扎入皮膚)Themembraneofthenervefibersintheskinisstretched(感覺神經(jīng)纖維的細(xì)胞膜被牽拉)Na+-permeablechannelsopen.TheentryofNa+depolarizesthemembrane(Na+通道打開，細(xì)胞膜產(chǎn)生去極化)Thecriticallevelofdepolarizationthatmustbecrossedinordertotriggeranactionpotentialiscalledthreshold(閾電位).Actionpotentialarecausedbydepolarizationofthemembranebeyondthreshold.GenerationofanactionpotentThedepolarizationthatcausesactionpotentialarisesindifferentwaysindifferentneurons

(引起去極化的不同方式):CausedbytheentryofNa+throughspecializedionchannelsthatsensitivetomembranestretching

(膜的牽拉)Ininterneurons,depolarizationisusuallycausedbyNa+entrythroughchannelsthataresensitivetoneurotransmitters(神經(jīng)遞質(zhì)的釋放)

releasedbyotherneurons3.Inadditiontothesenaturalroutes,neuronscanbedepolarizedbyinjectingelectricalcurrent(注入電流)throughamicroelectrode,amethodcommonlyusedbyneuroscientiststostudyactionpotentialsindifferentcells. Applyingincreasingdepolarizationtoaneuronhasnoeffectuntilitcrossesthreshold,andthen“pop”–oneactionpotential.Forthisreason,actionpotentialsaresaidtobe“all-or-none”(全或無(wú)現(xiàn)象).ThedepolarizationthatcausesThegenerationofmultipleactionpotentialsContinuousdepolarizingcurrentManyactionpotentialsinsuccession注入電流ThegenerationofmultipleactThefiringfrequencyofactionpotentialsreflectsthemagnitudeofthedepolarizingcurrent

(頻率反應(yīng)去極化電流的大小)Thisisonewaythatstimulationintensityisencodedinthenervoussystem(中樞神經(jīng)系統(tǒng)編碼刺激強(qiáng)度的一種方式)ThefiringfrequencyofactionThoughfiringfrequencyincreaseswiththeamountofdepolarizingcurrent,thereisalimittotherateatwhichaneuroncangenerateactionpotentials.Absoluterefractoryperiod(絕對(duì)不應(yīng)期)Onceanactionpotentialisinitiated,itisimpossibletoinitiateanotherforabout1ms(動(dòng)作電位產(chǎn)生后1ms,不可能產(chǎn)生別的動(dòng)作電位)Relativerefractoryperiod(相對(duì)不應(yīng)期)Theamountofcurrentrequiredtodepolarizetheneurontoactionpotentialthresholdiselevatedabovenormal(絕對(duì)不應(yīng)期之后的幾個(gè)ms,需要比正常更大的閾電流才能爆發(fā)動(dòng)作電位)50ThoughfiringfrequencyincreaChapter4TheActionPotentialPROPERTIESOFTHEACTIONPOTENTIALTheUpsandDownsofanActionPotentialsGenerationofanActionPotentialTheGenerationofMultipleActionPotentialsTHEACTIONPOTENTIALINTHEORYMembraneCurrentsandConductancesTheInsandOutsofActionPotentialTHEACTIONPOTENTIALINREALITYTheVoltage-GatedSodiumChannelVoltage-GatedPotassiumChannelsPuttingthePiecesTogetherACTIONPOTENTIALCONDUCTIONFactorinfluencingconductionvelocityACTIONPOTENTIALS,AXONS,ANDDENDRITESCONCLUDINGREMARKSChapter4TheActionPotentiaTHEACTIONPOTENTIALINTHEORYDepolarizationofthecellduringtheactionpotentialiscausedbytheinfluxofsodiumionsacrossthemembrane(去極化是鈉離子內(nèi)流造成的)Repolarizationiscausedbytheeffluxofpotassiumions(復(fù)極化是鉀離子外流造成的)THEACTIONPOTENTIALINTHEORYTheInsandOutsofActionPotentialTherisingphase

AverylargedrivingforceonNa+

(-80-62)mV=-142mV

ThemembranepermeabilitytoNa+

>K+Depolarizationofthemembranebeyondthreshold,membranesodiumchannelsopened.ThiswouldallowNa+toentertheneuron,causingamassivedepolarizationuntilthemembranepotentialapproachedENa.Thefallingphase

ThedominantmembraneionpermeabilitytoK+K+flowoutofthecelluntilthemembranepotentialapproachedEK.TheInsandOutsofActionPotTheinsandoutsandupsanddownsoftheactionpotentialinanidealneuronisshownasbelow:(Fig4.5)Theinsandoutsandupsandd5555Chapter4TheActionPotentialPROPERTIESOFTHEACTIONPOTENTIALTheUpsandDownsofanActionPotentialsGenerationofanActionPotentialTheGenerationofMultipleActionPotentialsTHEACTIONPOTENTIALINTHEORYMembraneCurrentsandConductancesTheInsandOutsofActionPotentialTHEACTIONPOTENTIALINREALITYTheVoltage-GatedSodiumChannelVoltage-GatedPotassiumChannelsPuttingthePiecesTogetherACTIONPOTENTIALCONDUCTIONFactorinfluencingconductionvelocityACTIONPOTENTIALS,AXONS,ANDDENDRITESCONCLUDINGREMARKSChapter4TheActionPotentiaVoltageclamp(電壓鉗)provestheabovetheory:Voltageclamp(電壓鉗)provestheTheVoltage-GatedSodiumChannel

(電壓門控的鈉離子通道)TheproteinformsaporeinthemembranethatishighlyselectivetoNa+ions(對(duì)Na+具有高度的選擇性).Theporeisopenedandclosedbychangesintheelectricalpotentialofthemembrane(Na+通道的開放和關(guān)閉具有電壓依從性).TheVoltage-GatedSodiumChannSodiumchannelstructure

(Na+通道的結(jié)構(gòu))CreatedfromasinglelongpolypeptideHas4distinctdomains,numberedI-IV.ThefourdomainsarebelievedtoclumptogethertoformaporebetweenthemEachdomainconsistsof6transmembranealphahelices,numberedS1-S6Thechannelhasporeloopsthatareassembledintoaselectivityfilter60Sodiumchannelstructure

(Na+Figure4.6Structureofthevoltage-gatedsodiumchannel(a)Howthesodiumchannelpolypeptidechainisbelievedtobewovenintothemembrane.Themoleculeconsistsoffourdomains,I-IV.Eachdomainconsistsof6alphahelices,whichpassbackandforthacrossthemembraneFigure4.6Figure4.6(b)AnexpandedviewofonedomainshowingthevoltagesensorofalphahelixS4andtheporeloop(red),whichcontributestotheselectivityfilter(c)Aviewofthemoleculeshowinghowthedomainsmayarrangethemselvestoformaporebetweenthem.電壓感受器Figure4.6(b)AnexpandedviewFigure4.7Whenthemembraneisdepolarizedtothreshold,themoleculetwistsintoaconfigurationthatallowsthepassageofNa+throughthepore.

ThevoltagesensorresidesinsegmentS4ofthemolecule.Inthissegment,positivelychargedaminoacidresiduesareregularlyspacedalongthecoilsofthehelix.

Thus,theentiresegmentcanbeforcedtomovebychangingthemembranepotential.DepolarizationpushesS4awayfromtheinsideofthemembrane,andthisconformationalchangeinthemoleculecausesthegatetoopen.Figure4.7WhenthemembraneisThepatch-clamp(膜片鉗)Method-40mV65Thepatch-clamp(膜片鉗)Method-Functionalpropertiesofthesodiumchannel(Na+通道的功能)TheyopenwithlittledelayTheystayopenforabout1msandthenclose(inactivate)Theycannotbeopenedagainbydepolarizationuntilthemembranepotentialreturnsto–65mV關(guān)閉開放失活去失活FunctionalpropertiesofthesFunctionalpropertiesofthesodiumchannelFigure4.9(c)Amodelforhowchangesintheconformationofthesodiumchannelproteinmightyielditsfunctionalproperties.Theclosed(關(guān)閉)channel;

Opens(開放)uponmembranedepolarization;

Inactivation(失活)occurswhenaglobularportionoftheproteinswingsupandoccludesthepore;

Deinactivation(去失活)occurswhentheglobularportionswingsawayandtheporeclosesbymovementofthetransmembranedomains關(guān)閉開放失活去失活FunctionalpropertiesofthesToxinsonthesodiumchannelTetrodotoxin(TTX,河豚毒素)andsaxitoxinChannel-blockingtoxinBatrachotoxin,veratridineandaconitineOpenthechannelsinappropriatelyOpenatmorenegativepotentialsOpenmuchlongerthanusualToxinsonthesodiumchannelTePuttingthePiecesTogether(page89)ThresholdRisingphaseOvershootFallingphaseUndershootAbsoluterefractoryperiodRelativerefractoryperiodPuttingthePiecesTogether(pFigure4.10Themolecularbasisoftheactionpotential70Figure4.10ThemolecularbasiChapter4TheActionPotentialPROPERTIESOFTHEACTIONPOTENTIALTheUpsandDownsofanActionPotentialsGenerationofanActionPotentialTheGenerationofMultipleActionPotentialsTHEACTIONPOTENTIALINTHEORYMembraneCurrentsandConductancesTheInsandOutsofActionPotentialTHEACTIONPOTENTIALINREALITYTheVoltage-GatedSodiumChannelVoltage-GatedPotassiumChannelsPuttingthePiecesTogetherACTIONPOTENTIALCONDUCTIONFactorinfluencingconductionvelocityACTIONPOTENTIALS,AXONS,ANDDENDRITESCONCLUDINGREMARKSChapter4TheActionPotentiaFigure4.11ActionpotentialconductionFigure4.11Actionpotentialconduction.Theentryofpositivechargeduringtheactionpotentialcausesthemembranejustaheadtodepolarizetothreshold(已經(jīng)興奮的膜部分通過(guò)局部電流“刺激”了未興奮的膜部分，使之出現(xiàn)動(dòng)作電位)AnactionpotentialpropagatesinonedirectionAnactionpotentialcanbegeneratedbydepolarizationateitherendoftheaxonandthereforepropagateineitherdirectionFigure4.11ActionpotentialcFactorsInfluencingConductionVelocityActionpotentialconductionvelocityincreaseswithincreasingaxonaldiameter(軸突的直徑)Axonalsizeandthenumberofvoltage-gatedchannelsinthemembranealsoaffectaxonalexcitability(軸突上鈉離子通道的密度).Temperature

(溫度)FactorsInfluencingConductionMyelinandSaltatoryConductionMyelin(髓鞘)SchwanncellsintheperipheralnervoussystemOligodendrogliainthecentralnervoussystemVoltage-gatedsodiumchannelsareconcentratedinthemembraneofthenodesofRanvier(郎飛結(jié))Inmyelinatedaxones,actionpotentialsskipfromnodetonode(Saltatoryconduction跳躍式傳導(dǎo))MyelinandSaltatoryConductioMyelinandSaltatoryConductionInmyelinatedaxones,actionpotentialsskipfromnodetonode(Saltatoryconduction)75MyelinandSaltatoryConductioChapter4TheActionPotentialPROPERTIESOFTHEACTIONPOTENTIALTheUpsandDownsofanActionPotentialsGenerationofanActionPotentialTheGenerationofMultipleActionPotentialsTHEACTIONPOTENTIALINTHEORYMembraneCurrentsandConductancesTheInsandOutsofActionPotentialTHEACTIONPOTENTIALINREALITYTheVoltage-GatedSodiumChannelVoltage-GatedPotassiumChannelsPuttingthePiecesTogetherACTIONPOTENTIALCONDUCTIONFactorinfluencingconductionvelocityACTIONPOTENTIALS,AXONS,ANDDENDRITESCONCLUDINGREMARKSChapter4TheActionPotentiaSpike-initiationzoneOnlymembranethatcontains

voltage-gatedsodiumchannelsiscapableofgeneratingactionpotential.Voltage-gatedsodiumchannels

Theaxons>ThedendritesTheaxons>ThecellbodiesThepartoftheneuronwhereanaxonoriginatesfromthesoma,theaxonhillock(軸丘),isoftenalsocalledthespike-initiationzone(動(dòng)作電位起始點(diǎn)).Spike-initiationzoneOnlymembFigure4.14MembraneproteinspecifythefunctionofdifferentpartsoftheneuronAcorticalpyramidalneuronAprimarysensoryneuronFigure4.14MembraneproteinsChapter4TheActionPotentialPROPERTIESOFTHEACTIONPOTENTIALTheUpsandDownsofanActionPotentialsGenerationofanActionPotentialTheGenerationofMultipleActionPotentialsTHEACTIONPOTENTIALINTHEORYMembraneCurrentsandConductancesTheInsandOutsofActionPotentialTHEACTIONPOTENTIALINREALITYTheVoltage-GatedSodiumChannelVoltage-GatedPotassiumChannelsPuttingthePiecesTogetherACTIONPOTENTIALCONDUCTIONFactorinfluencingconductionvelocityACTIONPOTENTIALS,AXONS,ANDDENDRITESCONCLUDINGREMARKSChapter4TheActionPotentiaNeuronalElectricActivitiesInclude:RestPotential(Chapter3)ActionPotential(Chapter4)LocalPotentialsPost-SynapticPotentialExcitatoryPost-SynapticPotentialInhibitoryPost-SynapticPotentialEnd-platePotentialReceptorPotential80NeuronalElectricActivitiesIKEYTERMSANDREVIEWQUESTIONSP72andP97KEYTERMSANDREVIEWQUESTIONSThanksThanksNeuronalElectricActivities

神經(jīng)元的電活動(dòng)主講教師劉風(fēng)雨萬(wàn)有神經(jīng)科學(xué)研究所、神經(jīng)生物學(xué)系NeuronalElectricActivities

神NeuronalElectricActivitiesInclude:RestPotential

(Chapter3)ActionPotential(Chapter4)LocalPotentialsPost-SynapticPotentialExcitatoryPost-SynapticPotentialInhibitoryPost-SynapticPotentialEnd-platePotentialReceptorPotentialNeuronalElectricActivitiesIChapter3

TheNeuronalMembraneatRestTheCASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTheMOVEMENTOFIONSDiffusionElectricityTheIONICBASISOFRESTINGMEMBRANEPOTENTIALEquilibriumPotentialTheDistributionofIonsAcrosstheMembraneRelativeIonPermeabilitiesofMembraneatRestTheImportanceofRegulatingtheExternalPotassiumConcentrationCONCLUDINGREMARKSChapter3

TheNeuronalMembranCytosolandExtracellularFluidWater:Itsunevendistributionofelectricalcharge,soH2OisapolarmoleculeIons:SaltdissolvesreadilyinwaterbecausethechargedportionsofthewatermoleculehaveastrongerattractionfortheionsthantheyhaveforeachotherCytosolandExtracellularFluiThePhospholipidMembrane(磷脂膜)Thelipidsoftheneuronalmembraneforming:abarriertowater-solubleionsabarriertowater頭端-極性磷酸鹽-親水尾端-非極性碳?xì)浠衔?疏水5ThePhospholipidMembrane(磷脂膜ProteinTheseproteinsprovideroutesforionstocrosstheneuronalmembrane.Therestingandactionpotentialsdependonspecialproteinsthatspanthephospholipidbilayer.ProteinTheseproteinsprovideProtein–AminoAcidsProtein–AminoAcidsThePeptideBond(肽鍵)and

aPolypeptide(多肽)ThePeptideBond(肽鍵)and

aPFigure3.6ProteinStructureTheprimarystructureThesecondarystructureThetertiarystructureThequaternarystructureEachofthedifferentpolypeptidescontributingtoaproteinwithquaternarystructureiscalledasubunit(亞基).Figure3.6ProteinStructureThChannelProteinsChannelproteinissuspendedinaphospholipidbilayer,withitshydrophobic

(疏水的)portioninsidethemembranehydrophilic

(親水的)endsexposedtothewateryenvironmentsoneithersideFigure3.7AMembraneIonChannel10ChannelProteinsChannelproteiTwoPropertiesofIonChannelsIonselectivity(離子選擇性)ThediameteroftheporeThenatureoftheRgroupsliningitGating(門控特性)Channelswiththispropertycanbeopenedandclosed-gatedbychangesinthelocalmicroenvironmentofthemembraneTwoPropertiesofIonChannelsIonPumps(離子泵)IonpumpsareenzymesthatusetheenergyreleasedbythebreakdownofATPtotransportcertainionsacrossthemembraneIonPumps(離子泵)IonpumpsareeChapter3

TheNeuronalMembraneatRestTHECASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTHEMOVEMENTOFIO