Question

All of the following must occur before a second action potential can begin, EXCEPT

A) the Na+ and K+ ions that moved in/out of the cell must move back to their original compartments.
B) the Na+ inactivation gate must open and the Na+ activation gate must close.
C) the absolute refractory period must occur.
D) A and B
E) none of the above

Answer 1

The refractory period in an action potential prevents a second action potential from occurring. However, before a second action potential can begin, the Na+ inactivation gate must open and the Na+ activation gate must close.

Step-by-step explanation:

The refractory period is a period of time during which another action potential cannot be initiated. There are two phases of the refractory period: the absolute refractory period and the relative refractory period. During the absolute refractory period, the voltage-gated Na+ channels are inactivated and cannot be opened again until they return to their resting state. This means that another action potential cannot start until the inactivation gate of the Na+ channel opens and the activation gate closes, which is option B. Therefore, the correct answer is D) A and B.