Neurotransmitter: A chemical substance released at the end of a nerve fiber by the arrival of a nerve impulse and, by diffusing across the synapse, causes the transfer of the impulse to another nerve fiber, a muscle fiber, or some other structure.
Action Potential: A temporary reversal of an electric polarization of the membrane of a nerve cell or muscle cell, involved in the transmission of impulses.
Neuron: An electrically excitable cell that communicates with other cells via specialized connections called synapses