14. Which of the following actions contributes to the repolarization of a neuron?
Answer: B
Opening of potassium channels to allow potassium to leave the neuron.
Repolarization of a neuron occurs primarily through the opening of potassium channels, which allows potassium ions to exit the cell, helping to restore the negative internal charge after depolarization.
A) Inhibition of sodium and potassium pumps to stop all ion movement into the neuron.
Inhibiting the sodium and potassium pumps would prevent the re-establishment of the resting membrane potential and hinder the repolarization process. This option is incorrect as it would disrupt ion balance and prolong depolarization rather than facilitating repolarization.
B) Opening of potassium channels to allow potassium to leave the neuron.
This option is correct because the opening of potassium channels is a key mechanism in repolarization. When these channels open, potassium ions flow out of the neuron, leading to a decrease in positive charge inside the cell and restoring the negative membrane potential.
C) Closing of both sodium and potassium channels to restrict the movement of ions into and out of the neuron.
Closing both sodium and potassium channels would halt ion movement, thereby preventing the necessary changes in membrane potential that occur during repolarization. This option is incorrect as it does not allow for the exit of potassium, which is essential for returning to resting potential.
D) Opening of sodium channels to allow sodium to enter the neuron.
Opening sodium channels leads to depolarization, not repolarization, as it allows positive sodium ions to flow into the neuron. This option is incorrect as it contradicts the process of repolarization, which requires the exit of potassium rather than the influx of sodium.
Conclusion
The correct answer is B, as the opening of potassium channels is essential for the repolarization of neurons by allowing potassium to exit, which restores the negative charge inside the cell. All other options either inhibit the necessary ionic movements or promote depolarization, failing to facilitate the repolarization process effectively.