Final answer:
An action potential is electrical and occurs when a neuron fires, causing sodium ions to flow in and temporarily reverse the polarity during depolarization. This signal is rapidly sent down the axon, taking approximately a millisecond.
Step-by-step explanation:
An action potential is electrical in nature. The neuron is more negative inside because of negatively charged molecules like proteins on the inside and cations like sodium (Na+) and potassium (K+) outside. As the neuron fires, there’s a temporary reversal in polarity as the axon undergoes depolarization as sodium ions (Na+) flow into the cell. The action potential travels down the axon, sending a signal down it. The whole thing takes about 1/1,000th of a second.