Dual Enrollment Psychology (PSY 200) Final Practice Exam 2026 - Free Psychology Practice Questions and Study Guide

The brief electrical charge that travels along a neuron when it fires is called an action potential. This impulse is an all-or-none event: if the neuron reaches the threshold, voltage-gated channels open and a rapid depolarization occurs, followed by repolarization, producing a spike of about the same strength every time. Once it starts, the action potential propagates along the axon by triggering the next segment to depolarize, so the signal travels without diminishing its amplitude (myelination can speed this up through saltatory conduction). The frequency of these spikes, not their size, carries information about stimulus intensity. This is different from the resting potential, which is the baseline negative charge inside the neuron when it isn’t firing, and from membrane potential, which describes the electrical difference across the membrane at any moment. Neurotransmitter release happens at the synapse as a chemical consequence of the action potential reaching the terminal.