Which structure is NOT part of the cardiac conduction system?

Which structure is NOT part of the cardiac conduction system?

• A. Tunica media
• B. SA node
• C. AV node
• D. Purkinje fibers

Answer: (A)

The heart’s electrical wiring is made up of tissues that generate and spread impulses to coordinate the heartbeat. The SA node acts as the natural pacemaker, the AV node delays the signal to allow proper filling, and Purkinje fibers rapidly conduct the impulse through the ventricles for synchronized contraction. The tunica media, however, is the muscular middle layer of blood vessel walls (arteries and veins), not part of the heart’s electrical conduction pathways. It doesn’t generate or propagate electrical impulses, so it does not participate in coordinating the heartbeat.

The heart’s electrical wiring is made up of tissues that generate and spread impulses to coordinate the heartbeat. The SA node acts as the natural pacemaker, the AV node delays the signal to allow proper filling, and Purkinje fibers rapidly conduct the impulse through the ventricles for synchronized contraction. The tunica media, however, is the muscular middle layer of blood vessel walls (arteries and veins), not part of the heart’s electrical conduction pathways. It doesn’t generate or propagate electrical impulses, so it does not participate in coordinating the heartbeat.