Which of the following actions allows for repolarization of a neuron?
A.
The inhibition of sodium and potassium pumps, stopping all ion movement into the neuron
B.
The opening of sodium channels, allowing sodium to enter the neuron
C.
The closing of both sodium and potassium channels to restrict movement of ions into and out of the neuron
D.
The opening of potassium channels allowing potassium to leave the neuron
The correct answer and Explanation is :
The correct answer is D. The opening of potassium channels allowing potassium to leave the neuron.
Explanation:
Repolarization is a crucial phase in the action potential of a neuron, which is the process that allows neurons to transmit signals. This phase occurs after the depolarization phase, during which sodium (Na⁺) channels open, allowing sodium ions to flow into the neuron. This influx of sodium ions causes the neuron’s membrane potential to become more positive.
Repolarization occurs when the neuron needs to return to its resting membrane potential after depolarization. This process primarily involves the movement of potassium ions (K⁺) out of the neuron. When potassium channels open, potassium ions flow out due to the concentration gradient and the electrochemical gradient, which helps restore the negative charge inside the neuron.
Let’s analyze the other options:
- A. The inhibition of sodium and potassium pumps, stopping all ion movement into the neuron: This action would prevent the maintenance of the resting membrane potential and disrupt repolarization, making it incorrect.
- B. The opening of sodium channels, allowing sodium to enter the neuron: This action promotes depolarization, not repolarization. When sodium channels are open, the neuron becomes more positive inside.
- C. The closing of both sodium and potassium channels to restrict movement of ions into and out of the neuron: Closing sodium channels would stop further depolarization, but without the opening of potassium channels to allow K⁺ to exit, repolarization cannot occur.
In summary, the opening of potassium channels is essential for repolarization as it enables potassium ions to exit the neuron, restoring the negative internal environment and preparing the neuron for subsequent action potentials. This is vital for the proper functioning of neuronal signaling and overall nervous system activity.