Which part of the cardiac cycle is reflected in the ECG?

The correct answer is that both atrial and ventricular cycles are reflected in the ECG. The ECG records the electrical activity of the heart, which includes the depolarization and repolarization events of both the atria and the ventricles.

During the cardiac cycle, the P wave on the ECG corresponds to atrial depolarization, which occurs when the atria contract to push blood into the ventricles. Following this, the QRS complex represents ventricular depolarization, which occurs just before the ventricles contract to pump blood out to the lungs and the rest of the body. Additionally, the T wave indicates ventricular repolarization, where the ventricular muscles recover after contraction.

Thus, the ECG captures the electrical events associated with both atrial and ventricular contraction, making it essential for assessing the overall electrical function and health of the heart. Recognizing this dual representation is crucial for understanding the cardiac cycle as depicted by the ECG.