205textnotes10 - - The absolute refractory period. It comes...

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- The absolute refractory period . It comes immediately after the action potential. During this period, it is impossible to excite the cell no matter how larger a stimulating current is applied. -The relative refractory period . It follows the absolute refractory period. During this period, it is possible to trigger an action potential only by applying a stimulus that is stronger than normal. Stimulus intensity is coded by the frequency of action potential (Figure 8-13) The Na + -K + -ATPase plays no direct role in the action potential. The pump just moves Na + and K + across the membrane against their concentration gradients to maintain internal ion concentrations. The amount of Na + that enters and K + that leaves during an action potential is very small and a neuron will continue to fire for an extended period of time even if the pump is blocked. The action potential can be conducted at rates that vary between 1 to 100 m/s. But it often lasts only 1 ms. The depolarization is spread by "local-circuit" current flow resulting from the potential difference between the active
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This note was uploaded on 12/26/2011 for the course KIN 205 taught by Professor Blaber during the Fall '09 term at Simon Fraser.

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