Answer:
b. an electrical signal that travels along the axon of a neuron.
Explanation:
An action potential is a nerve impulse or an electrical signal that travels down an axon which cause a change in polarity across the membrane of the axon.
In response to an electrical signal from another neuron, sodium ion (Na+) and potassium ion (K+) (i.e gated ion channels) open and close as the membrane reaches its threshold potential. Na+ channels open at the beginning of the action potential, and Na+ moves into the axon, causing depolarization.
Repolarization occurs when the K+ channels open and K+ moves out of the axon, causing a diferent change in polarity between the exterior of the cell and the interior of the cell. The impulse then travels down the axon in one direction only, to the axon terminal where it signals to other neurons.
