At the end of the rising phase of an action potential,
A) a vast majority of the voltage-gated sodium channels begin to close.
B) the membrane potential shifts back toward the resting membrane potential.
C) the voltage-gated sodium channels enter a refractory period.
D) many more potassium channels begin to close.
E) a, b, and c

Question

Quizplus · Accepted Answer

At the end of the rising phase of an action potential, a vast majority of voltage-gated sodium channels begin to close (A). This causes the membrane potential to shift back toward the resting membrane potential (B) and the voltage-gated sodium channels enter a refractory period where they cannot be opened again for a brief period of time, contributing to the unidirectional propagation of the action potential (C). In addition, many more potassium channels begin to open (not close as stated in option D), which contributes to the falling phase of the action potential. Therefore, choices A, B, and C are all correct and make E the best answer.

At the End of the Rising Phase of an Action