What follows depolarization of the heart?

Following depolarization of the heart, the most immediate physiological response is the contraction of the heart muscle. Depolarization refers to the change in membrane potential that occurs when cardiac muscle cells become excited, leading to an influx of sodium ions and a subsequent increase in intracellular calcium levels. This process triggers the actin and myosin filaments in the muscle cells to interact, resulting in contraction.

This contraction is crucial for the mechanics of the heart; it enables the heart to pump blood effectively throughout the body. Each heartbeat begins with depolarization initiated by the pacemaker cells in the sinoatrial (SA) node, which stimulates the entire heart muscle to contract in a coordinated fashion.

While relaxation of the heart muscle does occur after contraction, it is a separate phase that follows the actual contraction. Likewise, an increase in heart rate is a potential outcome of sustained depolarization but does not directly follow a single repolarization event. Blood ejection from the atria involves a different phase of the cardiac cycle that takes place after the atrial contraction is complete, rather than being a direct response to depolarization.