Which waveform represents the P wave?

Which waveform represents the P wave?

• A. QRS complex represents Ventricular depolarization
• B. P wave represents Atrial depolarization
• C. T wave represents Repolarization
• D. U wave represents Ventricular repolarization

Answer: (B)

The P wave represents atrial depolarization: it marks the electrical activation spreading through the atria from the SA node, which triggers atrial contraction. On the ECG this shows up as a small, smooth deflection that occurs right before the larger QRS complex, which corresponds to ventricular depolarization. The T wave that follows represents ventricular repolarization, the ventricles resetting after contraction, and a U wave (when seen) is a small, less consistent deflection after the T wave and is not the primary indicator of ventricular repolarization.

The P wave represents atrial depolarization: it marks the electrical activation spreading through the atria from the SA node, which triggers atrial contraction. On the ECG this shows up as a small, smooth deflection that occurs right before the larger QRS complex, which corresponds to ventricular depolarization. The T wave that follows represents ventricular repolarization, the ventricles resetting after contraction, and a U wave (when seen) is a small, less consistent deflection after the T wave and is not the primary indicator of ventricular repolarization.