What does the P wave on an ECG correspond to?

The P wave on an electrocardiogram (ECG) corresponds to atrial depolarization. This is the electrical activity that triggers the contraction of the atria, leading to the filling of the ventricles with blood. When the atria depolarize, the electrical impulse spreads through the atrial muscle, causing them to contract and push blood into the ventricles.

Understanding the sequence of electrical events in the heart is crucial for interpreting an ECG. The P wave is the first deflection seen on the ECG tracing, indicating the start of the cardiac cycle with atrial activity. This is essential for maintaining the proper sequence of heart contractions and ensuring efficient blood flow through the heart chambers.

The other options do not accurately describe the P wave: ventricular depolarization is represented by the QRS complex, while atrial repolarization generally occurs simultaneously with the QRS complex but is not clearly represented on the standard ECG tracing. Ventricular repolarization is depicted by the T wave. Hence, the identification of the P wave as indicative of atrial depolarization is a fundamental concept in cardiac physiology.