During which phase does atrial depolarization occur?

Atrial depolarization corresponds with the P wave in an electrocardiogram (ECG). This phase represents the electrical activity that triggers the contraction of the atria, leading to the filling of the ventricles with blood. The P wave reflects the spread of electrical impulse through the atrial muscle, highlighting this crucial moment in the cardiac cycle.

The other phases represented in the ECG serve different functions: the QRS complex indicates the depolarization of the ventricles which leads to ventricular contraction, the T wave represents ventricular repolarization, and the U wave is often considered a reflection of the repolarization of the Purkinje fibers or other aspects of cardiac repolarization but is not directly associated with atrial activity. Understanding these phases is integral for recognizing the electrical events of the heart during each heartbeat.