Question

The falling phase of the action potential is due primarily to

A) Na+ flow in the cell.
B) Na+ flow out of the cell.
C) K+ flow out of the cell.
D) K+ flow into the cell.
E) B and D

Answer 1

The falling phase of the action potential is primarily due to the outflow of K+ ions from the cell during repolarization, which is crucial for nerve cell communication. The correct option is C) K+ flow out of the cell.

Step-by-step explanation:

The falling phase of the action potential is due primarily to K+ flow out of the cell. During depolarization, a stimulus causes membrane permeability to increase for Na+ ions, which flow into the cell. Repolarization follows as Na+ channels close and K+ channels open, allowing potassium ions to flow out from the cell's high concentration to a lower concentration outside, which aids in returning the membrane potential back towards the resting state and sometimes leads to a temporary hyperpolarization.

After the action potential, active transport mechanisms, such as the Na+/K+ pump, work to restore the ion concentration gradient, thus maintaining the resting potential in the long term and readying the cell for subsequent action potentials. These processes are fundamental to nerve cell communication and are critical for the proper functioning of the nervous system.

The correct option is C) K+ flow out of the cell.