What does ventricular depolarization initiate in the heart?

What does ventricular depolarization initiate in the heart?

• A. Atrial contraction
• B. Ventricular contraction
• C. Atrial repolarization
• D. Ventricular repolarization

Answer: (B)

Ventricular depolarization leads to the contraction of the ventricles, a process that is essential for the effective pumping of blood throughout the body. This phase of the cardiac electrical cycle corresponds with the QRS complex on an EKG, which reflects the electrical activity that triggers the myocardial cells in the ventricles to contract. As a result, blood is forcefully ejected from the ventricles into the aorta and pulmonary artery, supporting circulation.

In contrast, atrial contraction occurs prior to ventricular depolarization, as the P wave on the EKG represents atrial depolarization. Atrial repolarization occurs as the ventricles begin to depolarize, but its effects are overshadowed on the EKG by the QRS complex. Ventricular repolarization, which is marked by the T wave on the EKG, follows ventricular contraction and is essential for the heart to reset before the next cycle begins. Therefore, the initiation of ventricular depolarization specifically correlates with ventricular contraction.