After Purkinje activation, how is the impulse distributed to the rest of the heart?

• A. SA node
• B. AV node
• C. Purkinje fibers
• D. Cell-to-cell communication throughout rest of cardiac tissue

Answer: (D)

After the Purkinje system activates, the impulse is distributed to the rest of the heart mainly through cell-to-cell electrical coupling in the ventricular myocardium. Once the impulse reaches the endocardial surface via Purkinje fibers, it spreads rapidly from cardiomyocyte to cardiomyocyte through gap junctions at intercalated discs, allowing a synchronized depolarization and contraction of the ventricles. The SA node and AV node set the rhythm and provide conduction to the ventricles, but the actual spread across the ventricular muscle after Purkinje activation is achieved by this direct cell-to-cell conduction. Purkinje fibers themselves deliver the impulse to the ventricular tissue, but the broad distribution relies on gap-junction-mediated propagation between heart muscle cells.