Advanced Placement (AP) Biology 2026 – 400 Free Practice Questions to Pass the Exam

An action potential in neuronal communication is defined as a neural impulse that travels down an axon. This phenomenon occurs when a neuron receives a sufficient stimulus, leading to a rapid change in membrane potential. Specifically, during an action potential, sodium channels open, allowing sodium ions to rush into the neuron, causing depolarization. This is followed by the opening of potassium channels, which allows potassium ions to exit the neuron, leading to repolarization. The action potential propagates along the axon, allowing the transmission of signals over long distances within the nervous system. The rapid change in voltage across the membrane is critical for the initiation and propagation of neuronal signaling, enabling communication between neurons and ultimately coordinating bodily functions.