What occurs during phase 0 of the cardiac cycle?

Phase 0 of the cardiac cycle is characterized by depolarization. During this phase, an action potential is initiated in cardiac myocytes, resulting in a rapid influx of sodium ions through voltage-gated sodium channels. This influx of sodium causes a significant change in the membrane potential, leading to depolarization, which is crucial for the conduction of electrical impulses through the heart.

This depolarization phase sets the stage for the subsequent contraction of the heart muscle, driving the heartbeat and ensuring proper blood flow throughout the body. It's important to understand that other phases of the cardiac cycle involve different processes such as repolarization, filling of the coronary arteries, or atrial contraction, but those events occur at other stages rather than phase 0. Thus, recognizing that phase 0 specifically relates to depolarization is vital for comprehending the overall mechanics of the electrical activity in the heart.