What do each of these represent: P Wave, QRS Wave, and T Wave?

• A. P Wave: ventricular depolarization, QRS Wave: atrial depolarization, T Wave: repolarization
• B. P Wave: atrial depolarization, QRS Wave: repolarization, T Wave: ventricular depolarization
• C. P Wave: atrial depolarization, QRS Wave: ventricular depolarization, T Wave: depolarization
• D. P Wave: atrial depolarization, QRS Wave: ventricular depolarization, T Wave: repolarization

Answer: (D)

An electrocardiogram reflects the heart’s electrical activity during the cycle, and each wave corresponds to a specific activation or recovery of heart muscle. The P wave shows atrial depolarization, meaning the atria are activating to contract. The QRS complex shows ventricular depolarization, as the ventricles—being larger—activate and contract. The T wave marks ventricular repolarization, the ventricles resetting electrically for the next beat. It’s helpful to remember that atrial repolarization does occur, but it’s hidden within the QRS complex and not seen as a separate wave. The other options mix up which chamber is activating or which phase is depolarization versus repolarization, so they don’t match the standard sequence of events seen on an ECG.