Question

Which one of the following ion channels opens to repolarize the neuronal membrane when an action potential is generated?

• A. Casuperscript{2+} channel
• B. Hsuperscript{+} channel
• C. Nasuperscript{+} channel
• D. Ksuperscript{+} channel

Hint:

During the action potential, the opening of Ksuperscript{+} channels is essential for repolarization, while Nasuperscript{+} and Casuperscript{2+} channels primarily contribute to depolarization.

Answer 1

The Correct Option is D

During an action potential, the membrane potential of a neuron rapidly depolarizes, followed by repolarization. Repolarization occurs primarily due to the opening of potassium (K⁺) channels. When these channels open, K⁺ ions flow out of the cell, making the inside of the cell more negative and returning the membrane potential to its resting state. Hence, statement (D) is correct.

- (A): The Ca²⁺ channel opens during the depolarization phase of the action potential, but it does not contribute significantly to repolarization. Therefore, statement (A) is incorrect.
- (B): The H⁺ channel is not involved in the generation or repolarization of action potentials in neurons. Thus, statement (B) is incorrect.
- (C): The Na⁺ channel opens during depolarization, allowing Na⁺ to flow into the cell, which causes the membrane potential to become more positive. It does not play a direct role in repolarization. Hence, statement (C) is incorrect.

Thus, the correct answer is (D).