Which of the following best describes the propagation of depolarization down an axon?

• A. The action potential travels as a wave of depolarization along the axon membrane.
• B. Depolarization occurs only at the axon hillock and does not travel.
• C. The action potential is initiated at the axon terminal and moves towards the cell body.
• D. Depolarization is a passive process that does not involve ion channels.

Answer: (A)

Verified step by step guidance

1. Understand the concept of an action potential: An action potential is a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane, primarily in neurons.
2. Recognize the role of ion channels: Depolarization involves the opening of voltage-gated sodium channels, allowing Na+ ions to enter the neuron, which changes the membrane potential.
3. Identify the starting point of an action potential: It typically begins at the axon hillock, where the threshold potential is reached, triggering the opening of ion channels.
4. Describe the propagation of depolarization: Once initiated, the action potential travels as a wave of depolarization along the axon membrane, moving from the axon hillock towards the axon terminal.
5. Clarify the direction and nature of propagation: The action potential does not move backwards towards the cell body, nor is it a passive process; it actively involves ion channels opening sequentially along the axon.