What does "depolarization" refer to in cardiac physiology?

In cardiac physiology, "depolarization" refers to the process by which cardiac muscle cells, specifically the myocardial cells, change their membrane potential, leading to the cells becoming electrically charged. During depolarization, there is a rapid influx of sodium ions (Na+) into the cells, causing a shift in the membrane potential from a negative to a positive value. This change is critical for the initiation of electrical impulses that lead to the contraction of the heart muscle.

Understanding depolarization is essential for grasping how the heart functions as a pump. It plays a pivotal role in the cardiac action potential, which is the fundamental electrical event that promotes heartbeats. When depolarization occurs in a large number of cardiac cells, it triggers a coordinated contraction throughout the heart muscle, ensuring effective pumping action.

The other choices do not accurately describe depolarization. Relaxation of heart muscles refers to a different phase of the cardiac cycle known as repolarization or diastole, where the muscle cells return to their resting state. While depolarization contributes to the conduction of electrical impulses, it is not the conduction itself but rather a precursor to the conduction process. Finally, the stabilization of heart rate is influenced by various factors, but it is not a direct