2.10-2.11 Synaptic transmission

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1、2.10-2.11Synaptictransmission2015年3月25日16:29IntroductionA.Twotypesofsynapses1.Electricalsynapses(gapjunctions):BidirectionalpermitspassivecurrentflowthroughopenporesthatinterconnectadjacentneuronsGapjunctions:connexonstoprovideaqueouschannelthatallowsforacurrentcarryingmoleculetopasdirectlyfro

2、mthecytoplasmofoneneuronstoanother.2.Chemicalsynapses:UnidirectionalenableintercellularcommunicationviathesecretionofchemicalmessengersthatmustdiffusethegapbetweenadjacentneuronsTransmitterbindingtoreceptorsPresynapticterminalPostsynapticterminalB.Electricalsynapse分区02.大脑科学的第1页C.Chemicalsynaps

3、e1.Sequenceofeventsinvolvedinchemicalneurotransmission1.thepresynapticterminalcontains:a.neurotransmitterthatissynthesizedandstoredinsynapticvesiclesb.apoolofvesiclesthatare“docked”alonganactivezoneinthepresynapticmembrane,poisedtofusewiththeplasmamembrane.Docksaredockedandreadytogowhenanactio

4、npotentialarrives.2.anactionpotentialinvadesthepresynapticterminal3.associatedchangeinmembranepotentialcausestheopeningofvoltage-gatedCa+channels4.becauseofthesteepconcentrationgradientforCa++acrosstheplasmamembrane,Ca++rushesintothepresynapticterminal.Extracellularfluid>insidethepresynapticte

5、rminal5.viaacascadeofmolecularevents,Ca++causesthefusionof“docked”vesicleswiththepresynapticplasmamembranealongthesynapticcleft6.vesiclefusionreleasesneurotransmitterintothesynapticcleft7.neurotransmitterdiffusesacrossthesynapticcleftandbindsspecificreceptorsinthepostsynapticmembrane8.bindingo

6、fneurotransmittercausestheopeningorclosingofionchannelsinthepostsynapticmembrane9.currentflowsthroughopenchannelsinthepostsynapticmembraneorthatmembranebecomesless“leaky”duetoclosureofcertainchannels;consequently,thepostsynapticmembranebecomeseitherdepolarizedorhyperpolarized:a.ifpositivecurre

7、ntflows(i.e.,cationsin)andthemembraneisdepolarized,voltage-gatedNa+channelswillopenandapostsynapticpotentialwillbegenerated;ifthresholdisreached,thepostsynapticneuronwillthenfireanactionpotential分区02.大脑科学的第2页potentialb.ifnegativecurrent