How does the action potential spread from the AV node?

How does the action potential spread from the AV node?

• A. Through the AV bundle to the Purkinje fibers
• B. Directly through the ventricular myocardium
• C. Via the bloodstream to the Purkinje fibers
• D. Across the atrial wall without specialized pathways

Answer: (A)

Conduction from the AV node uses a specialized His-Purkinje system designed for rapid, coordinated ventricular activation. After the AV node, the impulse travels into the Bundle of His, which runs through the interventricular septum and then divides into the right and left bundle branches. These branches deliver the impulse to Purkinje fibers that spread it quickly throughout the ventricular myocardium, producing synchronous depolarization and contraction of the ventricles. This pathway is essential because it coordinates the timing of ventricular squeeze, following the AV node’s delay that allows enough time for atrial filling. Other routes—such as moving directly through ventricular muscle, traveling via the bloodstream, or crossing the atrial wall without this specialized wiring—would be much slower or ineffective at achieving synchronization.

Conduction from the AV node uses a specialized His-Purkinje system designed for rapid, coordinated ventricular activation. After the AV node, the impulse travels into the Bundle of His, which runs through the interventricular septum and then divides into the right and left bundle branches. These branches deliver the impulse to Purkinje fibers that spread it quickly throughout the ventricular myocardium, producing synchronous depolarization and contraction of the ventricles. This pathway is essential because it coordinates the timing of ventricular squeeze, following the AV node’s delay that allows enough time for atrial filling. Other routes—such as moving directly through ventricular muscle, traveling via the bloodstream, or crossing the atrial wall without this specialized wiring—would be much slower or ineffective at achieving synchronization.