Which component of the conduction system coordinates ventricular contraction?

• A. SA Node
• B. AV Node
• C. Bundle of His
• D. Purkinje fibers

Answer: (D)

The ventricle-wide, synchronized contraction is produced by the fastest conducting pathway that distributes the impulse across the ventricular muscle. After the impulse reaches the ventricles, it travels through the Purkinje fiber network, which spreads rapidly throughout the ventricular endocardium to stimulate the majority of ventricular myocytes almost simultaneously. This rapid, coordinated activation ensures both ventricles contract together and eject blood efficiently.

The SA node sets the pace for the heart and drives atrial contraction, while the AV node introduces a brief delay to allow atrial emptying and ventricular filling. The Bundle of His serves as the conduit that carries the impulse into the ventricles, but the quick, widespread activation needed for synchronized ventricular contraction comes from the Purkinje fibers.