2026 Dual Enrollment Biology Complete Practice Test

Voltage-gated ion channels control the electrical signal by opening and closing in response to changes in membrane potential, changing the membrane’s permeability to specific ions. When a neuron reaches threshold, voltage-gated sodium channels open to allow Na+ to rush in, causing rapid depolarization. These channels then inactivate, and voltage-gated potassium channels open to let K+ out, driving repolarization. The sequential opening of channels along the axon creates a traveling wave of depolarization, propagating the action potential. Other options miss this gating mechanism or describe processes that aren’t how action potentials are generated.