Question

Which of the following would cause depolarization (an action potential) of a membrane?

A. Allow K+ to leave the cell
B. Allow Cl- to enter the cell
C. Allow Na+ to enter the cell
D. All of the above

Answer 1

Depolarization of a neuron's membrane leading to an action potential is caused by the entry of Na+ ions when voltage-gated sodium channels open in response to a stimulus.

Step-by-step explanation:

The depolarization of a neuron's membrane, which leads to an action potential, is primarily caused by Na+ ions entering the cell. This inflow of sodium occurs when voltage-gated sodium channels open in response to a stimulus, allowing Na+ ions to rush into the neuron. This causes the membrane potential to become less negative, moving towards the threshold that triggers an action potential.

Once the threshold is reached, more sodium channels open, resulting in a rapid influx of Na+ ions, which further depolarizes the membrane. This sudden change in voltage is what constitutes the action potential. Following the peak of the action potential, K+ channels open, allowing potassium ions to flow out of the neuron, repolarizing and restoring the membrane potential towards its resting state.