The P wave on an ECG represents electrical changes of atrial depolarization at which location?

The P wave on an ECG represents electrical changes of atrial depolarization at which location?

• A. SA node
• B. AV node
• C. Purkinje fibers
• D. Endocardium

Answer: (A)

Atrial depolarization starts in the sinoatrial node, the heart’s natural pacemaker located in the right atrium near the opening of the superior vena cava. The electrical impulse from the SA node spreads through the atrial myocardium, and this wave of depolarization is what the P wave represents on the ECG. The AV node sits along the path and introduces a brief delay before the ventricles depolarize, which shows up as the PR interval, not the P wave. Purkinje fibers and ventricular depolarization produce the QRS complex, while the endocardium is just the inner lining and does not generate the depolarization seen as the P wave.

Atrial depolarization starts in the sinoatrial node, the heart’s natural pacemaker located in the right atrium near the opening of the superior vena cava. The electrical impulse from the SA node spreads through the atrial myocardium, and this wave of depolarization is what the P wave represents on the ECG. The AV node sits along the path and introduces a brief delay before the ventricles depolarize, which shows up as the PR interval, not the P wave. Purkinje fibers and ventricular depolarization produce the QRS complex, while the endocardium is just the inner lining and does not generate the depolarization seen as the P wave.