The falling phase of the action potential is due primarily to
A) Na⁺ flow in the cell only.
B) Na⁺ flow out of the cell only.
C) K⁺ flow out of the cell only.
D) K⁺ flow into the cell only.
E) Na⁺ flow out of the cell and K⁺ flow into the cell.

Question

Quizplus · Accepted Answer

The falling phase of the action potential is due primarily to K⁺ flow out of the cell. This is because after the peak of the action potential, the voltage-gated K⁺ channels open, allowing K⁺ to move out of the cell, causing the membrane potential to become more negative and leading to the repolarization of the cell. While Na⁺ flow into the cell is responsible for depolarization, it is not involved in the falling phase of the action potential. Therefore, the correct answer is C, K⁺ flow out of the cell only.

The Falling Phase of the Action Potential Is Due Primarily