Neural Signaling: Postsynaptic Potentials Lesson 8

Neural Signaling: Within neuron Electrical signal Dendrites & soma postsynaptic potentials (PSP) passive current Axon action potentials (AP) propagated / regenerated ~

Postsynaptic Potentials Synapse Presynaptic neuron Postsynaptic neuron

Postsynaptic Potentials - PSPs Changes in Em Chemically-gated ion channels neurotransmitters PSP characteristics Graded Summation Fast Decremental ~

Post-synaptic Potentials Generation of PSP NT binds to receptor specific ion channels open ion moves according to gradients Neural signal Na+ influx  excitation ( AP) K+ efflux  inhibition ( AP) ~

EPSPs Excitatory Postsynaptic Potential Na+ influx Depolarization (+) Em becomes more positive APs more likely ~

Record here EPSP + + 0 mV Em - 70 mV AT REST - Time

IPSPs Inhibitory Postsynaptic Potential K+ efflux hyperpolarization (-) Em becomes more negative APs less likely similar to EPSPs EXCEPT opposite ~

IPSP - + Em - 70 mV AT REST - Time

Integration: Summation Temporal summation repeated stimulation at same synapse(s) Spatial summation stimulation from multiple synapses EPSPs & IPSPs summate a maximum for both ~

Em Temporal + Summation + - Repeated stimulation same synapse ~ Time 0 mV Em - 70 mV AT REST - Time

Em Temporal + Summation + - more depolarization Time 0 mV - 70 mV AT REST - Time

Em Spatial + Summation + + - Multiple synapses Time 0 mV - 70 mV AT REST - Time

EPSPs & IPSPs summate Net stimulation EPSPs + IPSPs = net effects Integration net effects = decision excitation inhibition  or  action potentials ~

+ EPSP IPSP - + - 70 mV -

Postsynaptic Potentials Soma & Dendrites Chemically-gated channels Passive current Graded Summation EPSP Excitatory Depolarization Na+ influx AP more likely IPSP Inhibitory Hyperpolarization K+ efflux AP less likely