Question

Absolute refractory period of neuron corresponds to

Answer 1

 At the peak of the action potential, all Na+ channels become inactivated. When Na+ channels are inactivated, they cannot be immediately opened again (see figure on Na+ channel inactivation). Recovery from inactivation is a time- and voltage-dependent process, and full recovery usually takes about 3-4 ms. Therefore, it takes about 3-4 ms for all Na+ channels to come out of inactivation in order to be ready for activation (opening) again. The period from the initiation of the action potential to immediately after the peak is referred to as the absolute refractory period (ARP) (see Figs. 1 and 2). This is the time during which another stimulus given to the neuron (no matter how strong) will not lead to a second action potential. Thus, because Na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials. The absolute refractory period takes about 1-2 ms.

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