Relative refractory periods can help us figure how intense a stimulus is - cells in your retina will send signals faster in bright light than in dim light, because the trigger is stronger. This means that the initial triggering event would have to be bigger than normal in order to send more action potentials along. It would take even more positive ions than usual to reach the appropriate depolarization potential than usual. However, the cell is still hyperpolarized after sending an action potential. This is the period after the absolute refractory period, when the h gates are open again. Relative refractory period: during this time, it is really hard to send an action potential.Absolute refractory periods help direct the action potential down the axon, because only channels further downstream can open and let in depolarizing ions. No sodium means no depolarization, which means no action potential. The inactivation (h) gates of the sodium channels lock shut for a time, and make it so no sodium will pass through. Absolute refractory period: during this time it is absolutely impossible to send another action potential.
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