Which of the following actions allows for repolarization of a neuron?

• A. Closing of potassium (K^+) leak channels
• B. Influx of calcium (Ca^{2+}) ions
• C. Opening of voltage-gated sodium (Na^+) channels
• D. Opening of voltage-gated potassium (K^+) channels

Answer: (D)

Verified step by step guidance

1. Understand the concept of repolarization: Repolarization is the process by which a neuron restores its resting membrane potential after depolarization. During depolarization, the inside of the neuron becomes more positive due to the influx of sodium (Na⁺) ions.
2. Recall the role of potassium (K⁺) in repolarization: Potassium ions play a key role in repolarization. When voltage-gated potassium channels open, potassium ions move out of the neuron, driven by their concentration gradient, which helps restore the negative charge inside the neuron.
3. Eliminate incorrect options: Closing potassium leak channels would prevent potassium from leaving the cell, hindering repolarization. Influx of calcium ions (Ca²⁺) is not directly involved in repolarization. Opening voltage-gated sodium channels causes depolarization, not repolarization.
4. Focus on the correct action: Opening voltage-gated potassium (K⁺) channels allows potassium ions to exit the neuron, reducing the positive charge inside the cell and restoring the resting membrane potential.
5. Summarize the mechanism: The opening of voltage-gated potassium channels is the key action that facilitates repolarization by allowing potassium ions to flow out of the neuron, re-establishing the negative resting potential.