Which components are part of the cardiac conduction system?

• A. Atrioventricular bundle and Purkinje system
• B. Aorta and ventricles
• C. Sinoatrial node and atrioventricular node only
• D. SA node, AV node, Bundle of His, Purkinje fibers

Answer: (D)

The heart’s conduction system is the specialized electrical network that generates and rapidly transmits impulses to coordinate each beat. It starts with the sinoatrial node, which acts as the natural pacemaker and sets the pace by initiating impulses that spread through the atria. The signal then reaches the atrioventricular node, which provides a brief delay to allow the atria to contract and the ventricles to fill. From there, the impulse travels down the Bundle of His, which conducts to the right and left bundle branches and ultimately into the Purkinje fibers that rapidly distribute the impulse through the ventricles, causing a synchronized contraction.

This full set—SA node, AV node, Bundle of His, and Purkinje fibers—is necessary to generate and propagate electrical activity through both atria and ventricles in a coordinated way. The aorta and the ventricles themselves are structures involved in pumping blood, not part of the electrical conduction pathway. If only the SA and AV nodes are considered, the rapid ventricular activation via the Purkinje network would be missing; if the bundle and Purkinje fibers are considered without the SA node, there’s no intrinsic pacemaking. The complete conduction system comprises all four components.