Question

What stops the rising phase of the action potential?

A) The sodium activation gate closes.
B) The Na+ inactivation gate opens.
C) The K+ gate closes.
D) The Na+ inactivation gate closes.
E) The Na+ activation gate opens.

Answer 1

The rising phase of an action potential is stopped by the closure of the Na+ inactivation gate, halting sodium entry into the cell and starting the process of repolarization.

Step-by-step explanation:

The rising phase of an action potential is stopped when the Na+ inactivation gate closes. During the depolarization phase, the activation gate of the voltage-gated Na+ channels opens, allowing Na+ to enter the cell, which causes the inside of the cell to become more positive.

However, timed with the peak of depolarization, the Na+ inactivation gate closes, preventing more Na+ from entering the cell and leading to the beginning of repolarization. Additionally, K+ channels open, allowing K+ to leave the cell, further aiding in returning the membrane potential towards the resting state.