Which structure conducts impulses into the ventricles?

• A. SA node
• B. Bundle of His
• C. Purkinje fibers
• D. AV node

Answer: (B)

Electrical conduction in the heart follows a specific pathway, and the entry of the impulse into the ventricles comes through a dedicated conduit that runs down the interventricular septum. After the impulse pauses briefly at the atrioventricular node, it travels via the bundle of His, which carries it from the AV node into the ventricles. From there, it splits into the right and left bundle branches and quickly reaches the Purkinje fibers to spread the impulse across the ventricular myocardium, producing a synchronized contraction.

This is why the bundle of His is the best answer: it serves as the direct link that transmits the impulse from the AV node into the ventricular tissue. The SA node initiates the signal in the atria, not into the ventricles. Purkinje fibers distribute the impulse within the ventricles after it has entered, rather than acting as the entry point from the AV node.