Question

Describe the three states of the Na+ channel during rest, depolarization, and repolarization of an excitable cell.

A. Closed during rest, open during depolarization, and closed during repolarization.
B. Open during rest, closed during depolarization, and open during repolarization.
C. Closed during rest, closed during depolarization, and open during repolarization.
D. Open during rest, open during depolarization, and closed during repolarization.

Answer 1

The Na+ channels are closed during rest, open during depolarization, and closed during repolarization of an excitable cell.

Step-by-step explanation:

The correct answer is A. Closed during rest, open during depolarization, and closed during repolarization.

During rest, the sodium (Na+) channels in an excitable cell are closed. When the cell depolarizes, meaning the membrane potential becomes more positive, the Na+ channels open to allow sodium ions to enter the cell. This influx of positive charge leads to the depolarization of the cell. During repolarization, the Na+ channels close again, restoring the resting state of the cell.