What physiological event does the P-wave represent?

The P-wave on an electrocardiogram (ECG) is a graphical representation of atrial depolarization, which leads to atrial contraction. During this phase, the electrical impulses generated by the sinoatrial (SA) node spread throughout the atria, causing them to contract and push blood into the ventricles. This event is crucial for maintaining an effective cardiac output, as it precedes the ventricular contraction that follows after a short delay indicated by the PR interval.

In contrast to the P-wave, the other options represent different physiological events. Ventricular contraction is indicated by the QRS complex, while ventricular repolarization is represented by the T-wave. Atrial repolarization also occurs, but its electrical activity is typically obscured by the QRS complex on the ECG. Understanding these patterns is essential for interpreting ECGs and recognizing normal heart rhythms and potential abnormalities.