Which component of the conduction system has the fastest conduction velocity?

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

Answer: (B)

Purkinje fibers have the fastest conduction velocity because they are large-diameter, highly connected cells that form a rapid, all-encompassing network to spread the impulse quickly throughout the ventricles. Their abundance of gap junctions and the low internal resistance between cells allow the action potential to propagate with minimal delay from cell to cell, delivering the signal to every ventricular region almost simultaneously. This rapid spread is essential for synchronized ventricular contraction.

In contrast, other parts of the conduction system are designed with deliberate slower conduction or pacing roles. The AV node slows the impulse to provide a delay between atrial contraction and ventricular activation, ensuring proper filling and timing. The SA node serves as the heart’s pacemaker and has slower conduction properties, while the Bundle of His conducts the impulse more quickly than the AV node but still slower than the Purkinje network, serving as a bridge to the ventricles.