The cardiac conduction system regulates which of the following?

• A. Blood pressure
• B. Respiratory rate
• C. Digestive pace
• D. Heart rhythm and contractions

Answer: (D)

The cardiac conduction system is the electrical highway that sets the pace and timing of the heartbeat, generating impulses and relaying them so the heart contracts in a coordinated rhythm. The SA node acts as the natural pacemaker, starting each impulse and causing atrial contraction. The impulse then travels to the AV node, which provides a slight delay to let the atria finish contracting, before moving to the His-Purkinje system to trigger ventricular contraction. This sequence produces a regular heart rhythm and synchronized atrial–ventricular contractions, which is what the system for regulating heart rhythm and contractions is all about.

Blood pressure, respiratory rate, and digestive pace are controlled by other systems: blood pressure depends on cardiac output and vascular resistance and is adjusted by autonomic and hormonal influences; respiratory rate by brainstem centers responding to gas levels; digestive pace by autonomic and enteric nervous system activity. None of these are the primary role of the cardiac conduction system.