HK 2810 Study Guide - Midterm Guide: Myosin Light-Chain Kinase, Resting Potential, Ganglion Cell

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The action potential is a single event occurring on one specific spot on the membrane of a neuron, but some neurons are a meter long. Answer: at resting potential (-70mv), the cell is unstimulated, having a separation of charge (-ve inside, +ve outside). When ap is generated at one point on membrane, it sets another separation of charge which causes bidirectional spread of charge from that point via local current. Local current decays over distance because there are protein pores that allows transmembrane leak and because not all ions move longitudinally. As it moves down the axon, adjacent patch of membrane depolarizes, causing voltage gated na+ channel to open and generate another ap. Action potential doesn"t go backward because there is brief period called refractory period when no ap can be generated even in presence of stimulus. The absolute refractory period is due to saturation of na+ channel or inactivation of na+ channel.