An action potential involves the temporary ________ through an axon membrane.

• A. loss of myelin sheath
• B. increase in neurotransmitter release
• C. decrease in synaptic vesicle formation
• D. reversal of membrane potential

Answer: (D)

Verified step by step guidance

1. Understand the concept of an action potential: An action potential is a rapid electrical signal that travels along the axon of a neuron. It is caused by the movement of ions across the neuron's membrane, leading to a temporary reversal of the membrane potential.
2. Recall the resting membrane potential: At rest, the inside of the neuron is negatively charged relative to the outside, typically around -70 mV. This is maintained by the sodium-potassium pump and the selective permeability of the membrane to ions.
3. Identify the key event during an action potential: During an action potential, there is a temporary reversal of the membrane potential. This occurs when voltage-gated sodium (Na⁺) channels open, allowing Na⁺ ions to rush into the cell, making the inside of the cell more positive (depolarization).
4. Understand the role of repolarization: After the peak of the action potential, voltage-gated potassium (K⁺) channels open, allowing K⁺ ions to exit the cell. This restores the negative charge inside the cell (repolarization).
5. Eliminate incorrect options: The loss of the myelin sheath, increase in neurotransmitter release, and decrease in synaptic vesicle formation are not directly related to the process of an action potential. The correct answer is the 'reversal of membrane potential,' which is the defining feature of an action potential.