Which of the following best describes what happens when an action potential occurs in a neuron?

• A. The membrane potential becomes more negative as Cl\(^-\) ions enter the neuron.
• B. A rapid depolarization of the membrane followed by repolarization due to the movement of Na\(^+\) and K\(^+\) ions across the membrane.
• C. The neuron releases neurotransmitters into the synaptic cleft without any change in membrane potential.
• D. The neuron stops conducting electrical signals and enters a refractory period.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the concept of an action potential. An action potential is a rapid electrical signal that travels along the membrane of a neuron. It is initiated by changes in the membrane potential due to the movement of ions across the membrane.
2. Step 2: Identify the key ions involved in generating an action potential. Sodium (Na\(^+\)) and potassium (K\(^+\)) ions play critical roles in this process. Chloride (Cl\(^-\)) ions are not primarily involved in the depolarization and repolarization phases of an action potential.
3. Step 3: Break down the phases of an action potential. During depolarization, Na\(^+\) channels open, allowing Na\(^+\) ions to rush into the neuron, making the membrane potential more positive. During repolarization, K\(^+\) channels open, allowing K\(^+\) ions to exit the neuron, restoring the membrane potential to a more negative value.
4. Step 4: Clarify the role of neurotransmitter release. While neurotransmitters are released into the synaptic cleft during communication between neurons, this process is separate from the generation of an action potential. The release of neurotransmitters occurs after the action potential reaches the axon terminal.
5. Step 5: Address the refractory period. After an action potential, the neuron enters a refractory period during which it temporarily cannot fire another action potential. This ensures that signals are transmitted in one direction along the neuron.