What allows the action potential to return to a repolarized state?

There are choices for this question namely:

a. K + leaks into cells.

b. Voltage-gated Na + channels become inactivated.

c. Voltage-gated K + channels become inactivated.

d. Na + reaches equilibrium across the neural membrane and stops leaking in.

e. Voltage-gated Na + channels close.

The correct answer is "voltage-gated Na + channels become inactivated". In the events concerning an action potential, the first event is a stimulus that depolarize the resting membrane potential up to the threshold. When the threshold is reached there will be opening of voltage gated Na + channels wherein sodium can enter the cell and make the membrane more positive therefore called depolarization. After depolarization, voltage gated Na + channels become inactivated and K + leaks out of the cell making the cell less negative hence repolarization. After which, more and more K + ions leaks out making the membrane more negative than the resting membrane potential hence hyperpolarization. When K + channels are inactivated, the cell membrane will eventually go back to its resting membrane potential.