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SignaltransductionmediatedG-proteincoupledcAMP-PKAIP3-Ca2+DG-PKCpathwayIntegrin1SectionElectricalPropertiesoftheCellCHENWenfang 2心电 MembraneRestingmembraneAction(nervecell,musclecell,glandLocal(receptorpotential;synaptic4RestingmembraneIntracellular5RestingmembraneRestingpotential(RP):aconstantpotentialdifferenceacrosstheplasmamembraneinabsenceofexcitatoryorinhibitorystimulation,withtheinsidenegativerelativetotheoutside.6RestingmembraneSkeletalSkeletalmusclecell:-Nervecell:-Smoothmusclecell:-Redbloodcell:-7Membrane8Ionicbasisoftherestingmembranepotential9IonicbasisofrestingDistributionofmajorionacrossthemembraneofa44PotassiummovementduetoelectrochemicalgradientHighK+HighK+--L--+-+
LowHighHigh-++-90mV-++KK+leakchannelK+Ionmovementduetoconcentration
Ionmovementduetoelectrical
In1902JuliusBernsteinusedtheNernstequationasthetheoreticalframeworkonwhichtodevelopthehypothesisthattherestingpotentialofneuronsisbasedontheselectivepermeabilityofthemembraneto K+equilibriumpotential,Nernst EK=ln+—=58log]R:universalgasconstantT:absolutetemperatureZ:thevalenceofionF:Faraday
EK=-90~-Na+equilibriumpotential,Low-Low-+
HighLowLowENa=+50~IonmovementduetoconcentrationIonmovementduetoelectricalGiantSquid(巨型枪乌贼 In1939,HodgkinandHodgkinandEm=-65~- EK=-
Valueofresting
EK=-75mV ENa=+55mVEm=-60mVConstantK+currentandNa+IonicbasisofrestingDistributionofmajorionacrosstheplasmamembraneofatypicalmusclecellConcentration,44IonicbasisofrestingActivityofNa+-K+pump(contributionforrestingmembranepotentialisabout2~16mV)
K+ ActionActionActionpotentialsarerapid,largealterationsinthepotentialthatspreadrapidlyalongthewholecellAction(Negativeafter-(Negativeafter-
(Positive(Positiveafter-
AfterThresholdTheThethresholdpotentialisthemembranepotentialtowhichamembranemustbedepolarizedtoinitiateanactionpotential.阈电位:能够爆发动作电位的临界膜KeyThresholdstimulus(阈刺激):Theminimumstimulusneededtoachieveanactionpotential.ActionGiantsquidThenodeofRanvierinaCatvisualSheepheartganglionLayer5pyramidalcellintheratactionpotentialAll-or-none(“全或无”现象):eventthat allyornotatall.Canpropagatelong Nosummation(不发生融合ActionInward
➔OutwardElectrochemicaldriving=Em-AtrestingmembraneDrivingforcefor=Em-=-70mV–=-Drivingforcefor=Em-=-70mV–(-=
Inward ➔OutwardAtovershootDrivingforcefor=Em-=+30mV–=-Drivingforcefor=Em-=+30mV–(-=IonicbasisofactionEENa=+50~ChangeinmembraneconductanceduringanactionpotentialmembranemembraneVoltageINa=GNa•(Em-
=
/
Changeinmembraneconductanceduringanactionpotential(Na+channel(Na+channel(K+channelChangeinmembraneconductanceduringanactionpotentialAtalllevelsofdepolarization,Na+channelsopenmorerapidlythanK+Thehigherlevelthedepolarization,thegreateramplitudetheGNaorChangesinmembranepotentialandchangesinmembranepermeabilitytoNa+andK+PositiveLocalPositivePositive depolarizedCharacteristicsoflocalNo“All-or-SpatialTemporalForexample:end-plateSpatialsummationandtemporalsummationElectrotonicPropagationofactionThepropagationofanactionpotentialinanunmyelinatedLocalcurrentDentriticDentriticBasicstructureofneuronPropagationofactionPropagationofanactionpotentialinamyelinatedSaltatoryconduction:TheinitiationofanactionpotentialinonenodeofRanvierdepolarizesthenextnode.Jum fromonenodetothenext.SaltatoryExcitationandExcitation:actionExcitablecell:cellsthatcanproduceactionpotential.Neuron;musclecell;glandcellExcitability:abilitytoproduceactionpotential.KeyThresholdthresholdvaluethesmallestintensitycapableofmembranetoproduceaction ChangeinexcitabilityduringanactionpotentialAbsoluteAbsoluterefractoryRelativeSupranormalSubnormalperiodChangeinexcitabilityduringanactionpotentialAbsoluterefractoryperiod:timeduringwhichanexcitablemembranecannotgenerateanactionpotentialinresponsetoanystimulus.Actione(Negative(Negativeafter-(Positiveafter-(Positiveafter-ChangeinexcitabilityduringanactionpotentialRelativerefractoryperiod:timeduringwhichexcitablemembranewillproduceactionpotentialonlytoastimulusofgreaterstrengththantheusualthresholdstrength.Actione(Negative(Negativeafter-(Positiveafter-(Positiveafter-ChangeinexcitabilityduringanactionpotentialSupranormalperiod:timeduringwhichexcitablemembranewillproduceactionpotentialinresponsetosubthresholdstimuli.Actione(Negative(Negativeafter-(Positiveafter-(Positiveafter-ChangeinexcitabilityduringanactionpotentialSubnormalperiod:timeduringwhichexcitablemembranewillproduceactionpotentialinresponsetosuprathresholdstimuli.Actione(Negative(Negativeafter-(Positiveafter-(Positiveafter-DefinitionofIonicbasisofPermeabilitytoK+andActivityofNa+-K+pump(contributionrestingmembranepotentialisaboutAP,ionicCharacteristicsofAll-or-none:eventthatoccurs allyornotatal
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