离子通道和神经元的电活动Neuronal-Electric-Activities课件

NeuronalElectricActivities

神经元的电活动主讲教师刘风雨万有神经科学研究所、神经生物学系NeuronalElectricActivities

神NeuronalElectricActivitiesInclude:RestPotential

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

TheNeuronalMembraneatRestTheCASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTheMOVEMENTOFIONSDiffusionElectricityTheIONICBASISOFRESTINGMEMBRANEPOTENTIALEquilibriumPotentialTheDistributionofIonsAcrosstheMembraneRelativeIonPermeabilitiesofMembraneatRestTheImportanceofRegulatingtheExternalPotassiumConcentrationCONCLUDINGREMARKSChapter3

TheNeuronalMembranCytosolandExtracellularFluidWater:Itsunevendistributionofelectricalcharge,soH2OisapolarmoleculeIons:SaltdissolvesreadilyinwaterbecausethechargedportionsofthewatermoleculehaveastrongerattractionfortheionsthantheyhaveforeachotherCytosolandExtracellularFluiThePhospholipidMembrane(磷脂膜)Thelipidsoftheneuronalmembraneforming:abarriertowater-solubleionsabarriertowater头端-极性磷酸盐-亲水尾端-非极性碳氢化合物-疏水5ThePhospholipidMembrane(磷脂膜ProteinTheseproteinsprovideroutesforionstocrosstheneuronalmembrane.Therestingandactionpotentialsdependonspecialproteinsthatspanthephospholipidbilayer.ProteinTheseproteinsprovideProtein–AminoAcidsProtein–AminoAcidsThePeptideBond(肽键)and

aPolypeptide(多肽)ThePeptideBond(肽键)and

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

(疏水的)portioninsidethemembranehydrophilic

(亲水的)endsexposedtothewateryenvironmentsoneithersideFigure3.7AMembraneIonChannel10ChannelProteinsChannelproteiTwoPropertiesofIonChannelsIonselectivity(离子选择性)ThediameteroftheporeThenatureoftheRgroupsliningitGating(门控特性)Channelswiththispropertycanbeopenedandclosed-gatedbychangesinthelocalmicroenvironmentofthemembraneTwoPropertiesofIonChannelsIonPumps(离子泵)IonpumpsareenzymesthatusetheenergyreleasedbythebreakdownofATPtotransportcertainionsacrossthemembraneIonPumps(离子泵)IonpumpsareeChapter3

TheNeuronalMembraneatRestTHECASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTHEMOVEMENTOFIONSDiffusionElectricityTHEIONICBASISOFRESTINGMEMBRANEPOTENTIALEquilibriumPotentialTheDistributionofIonsAcrosstheMembraneRelativeIonPermeabilitiesofMembraneatRestTheImportanceofRegulatingtheExternalPotassiumConcentrationCONCLUDINGREMARKSChapter3

TheNeuronalMembranTHEMOVEMENTOFIONSAchannelacrossamembraneislikeabridgeacrossariver.AnopenchannelAnetmovementofionsacrossthemembrane.Ionmovementrequiresthatexternalforcesbeappliedtodriveionsacross.Twofactorsinfluenceionmovementthroughchannels:Diffusion(扩散)Electricity

(电势差)THEMOVEMENTOFIONSAchannelDiffusionTemperature-dependentrandommovementofionsandmoleculestendstodistributetheionsevenlythroughoutthesolutionsothatthereisanetmovementofionsfromregionsofhighconcentrationtoregionsoflowconcentration.Thismovementiscalleddiffusion

(扩散).Adifferenceinconcentrationiscalledaconcentrationgradient

(浓度梯度).15DiffusionTemperature-dependentFigure3.8DiffusionDrivingionsacrossthemembranebydiffusionhappenswhenThemembranepossesseschannelspermeabletotheionsThereisaconcentrationgradientacrossthemembraneFigure3.8DiffusionDrivingioElectricityAnotherwaytoinduceanetmovementofionsinasolutionistouseanelectricalfield(电场),becauseionsareelectricallychargedparticles.Oppositechargesattractandlikechargesrepel.ElectricityAnotherwaytoinduFigure3.9

ThemovementofionsinfluencedbyanelectricalfieldOppositechargesattractandlikechargesrepelFigure3.9

ThemovementofioElectricityTwoimportantfactorsdeterminehowmuchcurrent(I)willflow:Electricalpotential(V,电势)Electricalconductance(g,电导)Electricalconductance

Electricalresistance(电阻,R=1/g)Ohm’slaw:I=gVElectricityTwoimportantfactoFigure3.10ElectricalcurrentflowacrossamembraneDrivinganionacrossthemembraneelectricallyrequiresThemembranepossesseschannelspermeabletotheionsThereisaelectricalpotentialdifferenceacrossthemembrane20Figure3.10ElectricalcurrentDiffusionandElectricityElectricalchargedionsinsolutiononeithersideoftheneuronalmembrane.(带电离子溶解在细胞膜两侧的溶液中)Ionscancrossthemembraneonlybyproteinchannel.(离子必须通过离子通道实现跨膜运动)Theproteinchannelscanbehighlyselectiveforspecificions.(离子通道对离子具有高度的选择性)Themovementofanyionthroughchanneldependsontheconcentrationgradientandthedifferenceinelectricalpotential

acrossthemembrane.(离子的跨膜运动依赖于膜两侧的浓度梯度和电位差)DiffusionandElectricityElectChapter3

TheNeuronalMembraneatRestTheCASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTheMOVEMENTOFIONSDiffusionElectricityTheIONICBASISOFRESTINGMEMBRANEPOTENTIALEquilibriumPotentialTheDistributionofIonsAcrosstheMembraneRelativeIonPermeabilitiesofMembraneatRestTheImportanceofRegulatingtheExternalPotassiumConcentrationCONCLUDINGREMARKSChapter3

TheNeuronalMembranThemembranepotential(膜电位)isthevoltageacrosstheneuronalmembraneatanymoment,representedbythesymbolmV.Microelectrode(微电极)andmVmeasurementTHEIONICBASISOFTHERESTINGMEMBRANEPOTENTIAL(静息电位)Themembranepotential(膜电位)iEstablishingEquilibriumPotential(平衡电位)Figure3.12EstablishingequilibriuminaselectivelypermeablemembraneNopotentialdifferenceVm=0mVThediffusionalforce=TheelectricalforceVm=-80mV20:1EstablishingEquilibriumPotenEquilibriumpotentialsTheelectricalpotentialdifferencethatexactlybalancesanionicconcentrationgradientiscalledanionicequilibriumpotential,orsimplyequilibriumpotential

(当离子移动所产生的电位差和离子移动所造成的浓度势能差平衡时，不再有离子的净移动，这时膜两侧的电位差称为离子的平衡电位)Generatingasteadyelectricalpotentialdifferenceacrossamembranerequires

Anionicconcentrationgradient

Selectiveionicpermeability25EquilibriumpotentialsTheelecBeforemovingontothesituationinrealneurons,fourimportantpointsshouldbemade:Largechangesinmembranepotentialarecausedbyminusculechangesinionicconcentrations(仅需要微小的离子浓度改变就可以引起膜电位大幅度的变化)100mM99.99999mMVm=-80mVVm=0mVBeforemovingontothesituatBeforemovingontothesituationinrealneurons,fourimportantpointsshouldbemade:2.Thenetdifferenceinelectricalchargeoccursattheinsideandoutsidesurfacesofthemembrane(膜内外两侧电荷的不同仅仅分布于膜的内外侧面，而不是分布于整个细胞的内外液)Figure3.13(5nm)BeforemovingontothesituatBeforemovingontothesituationinrealneurons,fourimportantpointsshouldbemade:Ionsaredrivenacrossthemembraneatarateproportionaltothedifferencebetweenthemembranepotentialandtheequilibriumpotential(离子的跨膜速率与膜电位和平衡电位的差值成正比).NetmovementofK+occursasthemembranepotentialdifferedfromtheequilibriumpotential.Thisdifference(Vm-Eion)iscalledtheionicdrivingforce(离子驱动力).Iftheconcentrationdifferenceacrossthemembraneisknownforanion,anequilibriumpotentialcanbecalculatedforthation(根据某离子膜两侧浓度的差值可以计算该离子的平衡电位).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(膜内外两侧的离子浓度梯度的形成依赖于离子泵的活动)Twoimportantionpumps:Thesodium-potassiumpump(钠钾泵)isanenzymethatbreaksdownATPinthepresenceofinternalNa+.Thecalciumpump(钙泵)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(血脑屏障)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细胞内记录细胞外记录示波器MethodsofRecordingActionPoTheUpsandDownsofanActionPotentials上升支（去极化）下降支（复极化）超射超极化激活后电位2ms-65mV45TheUpsandDownsofanActionGenerationofanactionpotentialTheperceptionofsharppainwhenathumbtackentersyourfootiscausedbythegenerationofactionpotentialsincertainnervefibersintheskin:Thethumbtackenterstheskin(图钉扎入皮肤)Themembraneofthenervefibersintheskinisstretched(感觉神经纤维的细胞膜被牵拉)Na+-permeablechannelsopen.TheentryofNa+depolarizesthemembrane(Na+通道打开，细胞膜产生去极化)Thecriticallevelofdepolarizationthatmustbecrossedinordertotriggeranactionpotentialiscalledthreshold(阈电位).Actionpotentialarecausedbydepolarizationofthemembranebeyondthreshold.GenerationofanactionpotentThedepolarizationthatcausesactionpotentialarisesindifferentwaysindifferentneurons

(引起去极化的不同方式):CausedbytheentryofNa+throughspecializedionchannelsthatsensitivetomembranestretching

(膜的牵拉)Ininterneurons,depolarizationisusuallycausedbyNa+entrythroughchannelsthataresensitivetoneurotransmitters(神经递质的释放)

releasedbyotherneurons3.Inadditiontothesenaturalroutes,neuronscanbedepolarizedbyinjectingelectricalcurrent(注入电流)throughamicroelectrode,amethodcommonlyusedbyneuroscientiststostudyactionpotentialsindifferentcells. Applyingincreasingdepolarizationtoaneuronhasnoeffectuntilitcrossesthreshold,andthen“pop”–oneactionpotential.Forthisreason,actionpotentialsaresaidtobe“all-or-none”(全或无现象).ThedepolarizationthatcausesThegenerationofmultipleactionpotentialsContinuousdepolarizingcurrentManyactionpotentialsinsuccession注入电流ThegenerationofmultipleactThefiringfrequencyofactionpotentialsreflectsthemagnitudeofthedepolarizingcurrent

(频率反应去极化电流的大小)Thisisonewaythatstimulationintensityisencodedinthenervoussystem(中枢神经系统编码刺激强度的一种方式)ThefiringfrequencyofactionThoughfiringfrequencyincreaseswiththeamountofdepolarizingcurrent,thereisalimittotherateatwhichaneuroncangenerateactionpotentials.Absoluterefractoryperiod(绝对不应期)Onceanactionpotentialisinitiated,itisimpossibletoinitiateanotherforabout1ms(动作电位产生后1ms,不可能产生别的动作电位)Relativerefractoryperiod(相对不应期)Theamountofcurrentrequiredtodepolarizetheneurontoactionpotentialthresholdiselevatedabovenormal(绝对不应期之后的几个ms,需要比正常更大的阈电流才能爆发动作电位)50ThoughfiringfrequencyincreaChapter4TheActionPotentialPROPERTIESOFTHEACTIONPOTENTIALTheUpsandDownsofanActionPotentialsGenerationofanActionPotentialTheGenerationofMultipleActionPotentialsTHEACTIONPOTENTIALINTHEORYMembraneCurrentsandConductancesTheInsandOutsofActionPotentialTHEACTIONPOTENTIALINREALITYTheVoltage-GatedSodiumChannelVoltage-GatedPotassiumChannelsPuttingthePiecesTogetherACTIONPOTENTIALCONDUCTIONFactorinfluencingconductionvelocityACTIONPOTENTIALS,AXONS,ANDDENDRITESCONCLUDINGREMARKSChapter4TheActionPotentiaTHEACTIONPOTENTIALINTHEORYDepolarizationofthecellduringtheactionpotentialiscausedbytheinfluxofsodiumionsacrossthemembrane(去极化是钠离子内流造成的)Repolarizationiscausedbytheeffluxofpotassiumions(复极化是钾离子外流造成的)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(电压钳)provestheabovetheory:Voltageclamp(电压钳)provestheTheVoltage-GatedSodiumChannel

(电压门控的钠离子通道)TheproteinformsaporeinthemembranethatishighlyselectivetoNa+ions(对Na+具有高度的选择性).Theporeisopenedandclosedbychangesintheelectricalpotentialofthemembrane(Na+通道的开放和关闭具有电压依从性).TheVoltage-GatedSodiumChannSodiumchannelstructure

(Na+通道的结构)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.电压感受器Figure4.6(b)AnexpandedviewFigure4.7Whenthemembraneisdepolarizedtothreshold,themoleculetwistsintoaconfigurationthatallowsthepassageofNa+throughthepore.

ThevoltagesensorresidesinsegmentS4ofthemolecule.Inthissegment,positivelychargedaminoacidresiduesareregularlyspacedalongthecoilsofthehelix.

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

Opens(开放)uponmembranedepolarization;

Inactivation(失活)occurswhenaglobularportionoftheproteinswingsupandoccludesthepore;

Deinactivation(去失活)occurswhentheglobularportionswingsawayandtheporeclosesbymovementofthetransmembranedomains关闭开放失活去失活FunctionalpropertiesofthesToxinsonthesodiumchannelTetrodotoxin(TTX,河豚毒素)andsaxitoxinChannel-blockingtoxinBatrachotoxin,veratridineandaconitineOpenthechannelsinappropriatelyOpenatmorenegativepotentialsOpenmuchlongerthanusualToxinsonthesodiumchannelTePuttingthePiecesTogether(page89)ThresholdRisingphaseOvershootFallingphaseUndershootAbsoluterefractoryperiodRelativerefractoryperiodPuttingthePiecesTogether(pFigure4.10Themolecularbasisoftheactionpotential70Figure4.10ThemolecularbasiChapter4TheActionPotentialPROPERTIESOFTHEACTIONPOTENTIALTheUpsandDownsofanActionPotentialsGenerationofanActionPotentialTheGenerationofMultipleActionPotentialsTHEACTIONPOTENTIALINTHEORYMembraneCurrentsandConductancesTheInsandOutsofActionPotentialTHEACTIONPOTENTIALINREALITYTheVoltage-GatedSodiumChannelVoltage-GatedPotassiumChannelsPuttingthePiecesTogetherACTIONPOTENTIALCONDUCTIONFactorinfluencingconductionvelocityACTIONPOTENTIALS,AXONS,ANDDENDRITESCONCLUDINGREMARKSChapter4TheActionPotentiaFigure4.11ActionpotentialconductionFigure4.11Actionpotentialconduction.Theentryofpositivechargeduringtheactionpotentialcausesthemembranejustaheadtodepolarizetothreshold(已经兴奋的膜部分通过局部电流“刺激”了未兴奋的膜部分，使之出现动作电位)AnactionpotentialpropagatesinonedirectionAnactionpotentialcanbegeneratedbydepolarizationateitherendoftheaxonandthereforepropagateineitherdirectionFigure4.11ActionpotentialcFactorsInfluencingConductionVelocityActionpotentialconductionvelocityincreaseswithincreasingaxonaldiameter(轴突的直径)Axonalsizeandthenumberofvoltage-gatedchannelsinthemembranealsoaffectaxonalexcitability(轴突上钠离子通道的密度).Temperature

(温度)FactorsInfluencingConductionMyelinandSaltatoryConductionMyelin(髓鞘)SchwanncellsintheperipheralnervoussystemOligodendrogliainthecentralnervoussystemVoltage-gatedsodiumchannelsareconcentratedinthemembraneofthenodesofRanvier(郎飞结)Inmyelinatedaxones,actionpotentialsskipfromnodetonode(Saltatoryconduction跳跃式传导)MyelinandSaltatoryConductioMyelinandSaltatoryConductionInmyelinatedaxones,actionpotentialsskipfromnodetonode(Saltatoryconduction)75MyelinandSaltatoryConductioChapter4TheActionPotentialPROPERTIESOFTHEACTIONPOTENTIALTheUpsandDownsofanActionPotentialsGenerationofanActionPotentialTheGenerationofMultipleActionPotentialsTHEACTIONPOTENTIALINTHEORYMembraneCurrentsandConductancesTheInsandOutsofActionPotentialTHEACTIONPOTENTIALINREALITYTheVoltage-GatedSodiumChannelVoltage-GatedPotassiumChannelsPuttingthePiecesTogetherACTIONPOTENTIALCONDUCTIONFactorinfluencingconductionvelocityACTIONPOTENTIALS,AXONS,ANDDENDRITESCONCLUDINGREMARKSChapter4TheActionPotentiaSpike-initiationzoneOnlymembranethatcontains

voltage-gatedsodiumchannelsiscapableofgeneratingactionpotential.Voltage-gatedsodiumchannels

Theaxons>ThedendritesTheaxons>ThecellbodiesThepartoftheneuronwhereanaxonoriginatesfromthesoma,theaxonhillock(轴丘),isoftenalsocalledthespike-initiationzone(动作电位起始点).Spike-initiationzoneOnlymembFigure4.14MembraneproteinspecifythefunctionofdifferentpartsoftheneuronAcorticalpyramidalneuronAprimarysensoryneuronFigure4.14MembraneproteinsChapter4TheActionPotentialPROPERTIESOFTHEACTIONPOTENTIALTheUpsandDownsofanActionPotentialsGenerationofanActionPotentialTheGenerationofMultipleActionPotentialsTHEACTIONPOTENTIALINTHEORYMembraneCurrentsandConductancesTheInsandOutsofActionPotentialTHEACTIONPOTENTIALINREALITYTheVoltage-GatedSodiumChannelVoltage-GatedPotassiumChannelsPuttingthePiecesTogetherACTIONPOTENTIALCONDUCTIONFactorinfluencingconductionvelocityACTIONPOTENTIALS,AXONS,ANDDENDRITESCONCLUDINGREMARKSChapter4TheActionPotentiaNeuronalElectricActivitiesInclude:RestPotential(Chapter3)ActionPotential(Chapter4)LocalPotentialsPost-SynapticPotentialExcitatoryPost-SynapticPotentialInhibitoryPost-SynapticPotentialEnd-platePotentialReceptorPotential80NeuronalElectricActivitiesIKEYTERMSANDREVIEWQUESTIONSP72andP97KEYTERMSANDREVIEWQUESTIONSThanksThanksNeuronalElectricActivities

神经元的电活动主讲教师刘风雨万有神经科学研究所、神经生物学系NeuronalElectricActivities

神NeuronalElectricActivitiesInclude:RestPotential

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

TheNeuronalMembraneatRestTheCASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTheMOVEMENTOFIONSDiffusionElectricityTheIONICBASISOFRESTINGMEMBRANEPOTENTIALEquilibriumPotentialTheDistributionofIonsAcrosstheMembraneRelativeIonPermeabilitiesofMembraneatRestTheImportanceofRegulatingtheExternalPotassiumConcentrationCONCLUDINGREMARKSChapter3

TheNeuronalMembranCytosolandExtracellularFluidWater:Itsunevendistributionofelectricalcharge,soH2OisapolarmoleculeIons:SaltdissolvesreadilyinwaterbecausethechargedportionsofthewatermoleculehaveastrongerattractionfortheionsthantheyhaveforeachotherCytosolandExtracellularFluiThePhospholipidMembrane(磷脂膜)Thelipidsoftheneuronalmembraneforming:abarriertowater-solubleionsabarriertowater头端-极性磷酸盐-亲水尾端-非极性碳氢化合物-疏水5ThePhospholipidMembrane(磷脂膜ProteinTheseproteinsprovideroutesforionstocrosstheneuronalmembrane.Therestingandactionpotentialsdependonspecialproteinsthatspanthephospholipidbilayer.ProteinTheseproteinsprovideProtein–AminoAcidsProtein–AminoAcidsThePeptideBond(肽键)and

aPolypeptide(多肽)ThePeptideBond(肽键)and

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

(疏水的)portioninsidethemembranehydrophilic

(亲水的)endsexposedtothewateryenvironmentsoneithersideFigure3.7AMembraneIonChannel10ChannelProteinsChannelproteiTwoPropertiesofIonChannelsIonselectivity(离子选择性)ThediameteroftheporeThenatureoftheRgroupsliningitGating(门控特性)Channelswiththispropertycanbeopenedandclosed-gatedbychangesinthelocalmicroenvironmentofthemembraneTwoPropertiesofIonChannelsIonPumps(离子泵)IonpumpsareenzymesthatusetheenergyreleasedbythebreakdownofATPtotransportcertainionsacrossthemembraneIonPumps(离子泵)IonpumpsareeChapter3

TheNeuronalMembraneatRestTHECASTOFCHEMICALSCytosolandExtracellularFluidThePhospholipidMembraneProteinTHEMOVEMENTOFIO