Which structure delays impulses from the SA node to allow the atria to completely empty before the ventricles contract?

Which structure delays impulses from the SA node to allow the atria to completely empty before the ventricles contract?

• A. Atrioventricular Node
• B. Sinoatrial Node
• C. Bundle of His
• D. Purkinje Fibers

Answer: (A)

Delaying conduction at a specific point in the heart’s electrical pathway ensures the atria finish their contraction and preload the ventricles before they contract. The structure that creates this purposeful delay is the atrioventricular node. It sits between the atria and ventricles and conducts impulses more slowly than the sinoatrial node, producing a short pause of about 0.1 second. This pause gives the atria time to empty into the ventricles, maximizing ventricular filling (preload). After this delay, the impulse moves onward to the Bundle of His, then to the bundle branches and Purkinje fibers to coordinate the ventricles’ contraction. The Sinoatrial node is the natural pacemaker that starts the impulse, not the pause itself, and the Bundle of His and Purkinje fibers are involved in rapid propagation to the ventricles rather than delaying the signal.

Delaying conduction at a specific point in the heart’s electrical pathway ensures the atria finish their contraction and preload the ventricles before they contract. The structure that creates this purposeful delay is the atrioventricular node. It sits between the atria and ventricles and conducts impulses more slowly than the sinoatrial node, producing a short pause of about 0.1 second. This pause gives the atria time to empty into the ventricles, maximizing ventricular filling (preload). After this delay, the impulse moves onward to the Bundle of His, then to the bundle branches and Purkinje fibers to coordinate the ventricles’ contraction. The Sinoatrial node is the natural pacemaker that starts the impulse, not the pause itself, and the Bundle of His and Purkinje fibers are involved in rapid propagation to the ventricles rather than delaying the signal.