PHGY 209 Study Guide - Midterm Guide: Excitatory Postsynaptic Potential, Inhibitory Postsynaptic Potential, Resting Potential

• School: McGill University
• Department: Physiology
• Course: PHGY 209
• Professor: Ann Wechsler

Document Summary

X y = from x to y. Epsp = excitatory post-synaptic potential ip p = i(cid:374)hi(cid:271)itor(cid:455) post-synaptic potential. Autonomic fibres: enteric nervous system + heart. Potential of v= -70mv comes from: membrane = capacitor in a circuit, membrane is selectively permeable to k+ a(cid:374)d slightl(cid:455), na+ Dominant permeability: leak k+ ion channels, always open, selective for k+ (smallest), driving e. p to -90mv concentration gradient (in out) opposes electrical gradient (out in) Electrochemical equilibrium btwn the 2 forces creates potential. Nernst equation: e(k+)=constant * log(ratio of [ion outside]/[ion inside] = -90mv, e(na+)= +50mv. Subtle factor: some leak na+ channels exist, let the ion flow in to drive equilibrium potential to 50mv. Displaced na+ and k+ is constantly recycled by na-k pumps (2k+ in, 3na+ out) Initial segment to presynaptic terminal, propagated 1 direction. All or nothing transient depolarization-hyperpolarization pulse @threshold of -50mv. Voltage gated na+ channel @axon membrane, starts opening at -50mv, raises it to +30mv.