5-Elec Signals Neurons Figs BW

Whats worse is that some sodium channels although not

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Unformatted text preview: ny potassium, are open. sodium is way out of equilibrium (high concentration outside than inside, inside is negative, sodium is a cation, sodium is strongly drawn into the cell when channel is open). at -70 it's 130 mV out of equlibrium. a strong inwardly directly force make sodium want to go in. 3 Na+ ADP+Pi Vm – Eion ≡ Driving Force (for cations, - is inward, + is outward) For Na+: -70 - 60 = - 130 mV (inward) For K+: -70 + 90 = + 20 mV (outward) for a cation (sodium, potassium), if membrane potential is negative, current is inward. current is movement of charge (ions). direction of cation/positive movement move into cell if expression is negative. if postive, cation move out of cell. sodium move inward (-130) potassium +20, move outward If Vm = -70 mV, neither ion is in equilibrium, so Na+ leaks in, K+ leaks out the result is that there's constant leakage of ions across membrane. and what's the force driving this movement? at equilibrium potential, by definition no net force making one ion move, which means at all other potential, there's a force that's making the ion move. the force is proportional to the difference between the membrane potential and the equilibrium potential. that term: the membrane potential minus equilibrium force is called driving force (the force that drive ions through channels). Na+/K+ pumps counteract ion leakage, maintaining gradients and Vm leakage undo work of sodium-potassium pump. so pump is responsible for generating but also restoring the membrane potential. the pump can contribute directly to membrane potential, electrogenic (make cell more negative). blueish line is potassium channel. Phylogeny of V-Gated Ion Channels calcium channel arise from mutation long ago, these 2 transmembrane subunit was elaborated by addition of 4 more subunits (see circle) to form a 6 transmembrane potassium channel. ksubv means v-gated potassium channel (see blue lines). most the v-gated potassium channel of made of tetramer of subunit (4 of them together). also have v-gated ca and sodium channel. the first evolve is calci...
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This document was uploaded on 03/09/2014 for the course EXSC 301 at USC.

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