The electrical current that travels down the axon of a neuron is known as an action potential. An action potential is a rapid, stereotyped electrical signal that propagates along the axon membrane, caused by the sequential depolarization and repolarization of the neuronal membrane. It is initiated at the axon hillock (or axonal initial segment), where a high concentration of voltage-gated sodium channels allows the membrane potential to reach a threshold and trigger the action potential. This electrical impulse then travels down the axon to the axon terminals, where it can trigger the release of neurotransmitters into the synapse
. The action potential propagates in one direction-from the soma towards the axon terminals-due to the refractory period of the membrane segments that have just fired, preventing backward conduction. In myelinated axons, the action potential "jumps" between nodes of Ranvier in a process called saltatory conduction, which increases conduction speed
. In summary, the electrical current traveling down the axon is the action potential, the fundamental signal by which neurons communicate
