Which components constitute the heart's electrical conduction pathway?

• A. Sinoatrial node; Atrioventricular node; Bundle of His; Left and Right bundle branches; Purkinje fibers.
• B. Aorta; Pulmonary artery; Pulmonary valve; Mitral valve.
• C. Veins; Arteries; Capillaries; Myocardium.
• D. Hemoglobin; Iron; Oxygen; Carbon dioxide.

Answer: (A)

The heart’s electrical conduction pathway is a specialized chain that coordinates when the heart muscle contracts. It starts in the Sinoatrial node, the natural pacemaker, which generates the initial impulse that causes the atria to contract. The signal then reaches the Atrioventricular node, where a brief delay lets the atria finish filling the ventricles before the ventricles are stimulated. From there, the impulse travels down the Bundle of His, which splits into the left and right bundle branches and carries the signal toward the ventricles. Finally, the Purkinje fibers distribute the impulse rapidly through the ventricular myocardium, producing a coordinated and almost simultaneous contraction of both ventricles.

Other options describe parts of the circulation or blood components, not the electrical system that drives the heartbeat. Therefore, the structures that form this conduction pathway are the SA node, AV node, Bundle of His, left and right bundle branches, and Purkinje fibers.