Why is the QRS complex larger than the P wave in an electrocardiogram (ECG)?

• A. The P wave represents ventricular depolarization, which is a smaller electrical event than atrial depolarization.
• B. The QRS complex represents atrial repolarization, which is a larger electrical event than atrial depolarization.
• C. The QRS complex represents ventricular depolarization, which involves more muscle mass than atrial depolarization.
• D. The P wave represents ventricular repolarization, which is a smaller electrical event than ventricular depolarization.

Answer: (C)

Verified step by step guidance

1. Understand the components of an electrocardiogram (ECG): The ECG is a graphical representation of the electrical activity of the heart. It consists of several waves, including the P wave, QRS complex, and T wave.
2. Identify the events represented by each wave: The P wave represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T wave represents ventricular repolarization.
3. Compare the muscle mass involved: Ventricular depolarization involves more muscle mass than atrial depolarization. The ventricles are larger and have thicker walls compared to the atria, resulting in a larger electrical event.
4. Relate electrical activity to wave size: The size of the wave on the ECG is proportional to the amount of electrical activity. Since ventricular depolarization involves more muscle mass, it generates a larger electrical signal, resulting in a larger QRS complex compared to the P wave.
5. Clarify common misconceptions: Ensure understanding that the P wave represents atrial depolarization, not ventricular repolarization, and the QRS complex represents ventricular depolarization, not atrial repolarization.