LE 48-5DendritesCell bodyNucleusAxon hillockAxonSignaldirectionPresynaptic cellMyelin sheathSynapticterminalsSynapsePostsynaptic cellFig. 48-14PostsynapticneuronSynapticterminalsof pre-synapticneurons5 µmFig. 48-15Voltage-gatedCa2+ channelCa2+1234SynapticcleftLigand-gatedion channelsPostsynapticmembranePresynapticmembraneSynaptic vesiclescontainingneurotransmitter56K+Na+Electron micrograph ofsynapsesA synaptic vesicle is studdedwith many different proteins.Fig. 48-16abE1E2PostsynapticneuronITerminal branchof presynapticneuronE20–70Threshold of axon ofpostsynaptic neuronRestingpotentialMembrane potential (mV)E1E1(a) Subthreshold, no summation(b) Temporal summationE1E1ActionpotentialIAxonhillockE1Fig. 48-16cdE1E2Membrane potential (mV)ActionpotentialIE1 + E2 (c) Spatial summation(d) Spatial summation of EPSP and IPSPE1E1E1 +
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