The normal conducting pathway sequence starting from the SA node includes these structures in order?

The normal conducting pathway sequence starting from the SA node includes these structures in order?

• A. SA node → Purkinje fibers → AV node → bundle of His
• B. SA node → AV node → bundle of His → right and left bundle branches → Purkinje fibers
• C. SA node → AV node → Purkinje fibers → bundle of His
• D. SA node → Purkinje fibers → bundle of His → AV node

Answer: (B)

The question tests understanding of the heart’s electrical conduction pathway and the order in which impulses travel from the SA node to the ventricles. The correct sequence starts at the SA node in the right atrium, then moves to the atrioventricular (AV) node where there is a brief delay to allow atrial contraction, then proceeds to the bundle of His (AV bundle) in the interventricular septum, then branches into the right and left bundle branches, and finally reaches the Purkinje fibers that distribute the impulse through the ventricles to coordinate contraction. This order is why this option is best: it keeps the AV node as the gateway after the SA node, follows with the His bundle, then the bundle branches, and ends with the Purkinje network. Other sequences place Purkinje fibers too early or skip the AV node and His bundle, which would disrupt the normal flow of excitation and timing of atrial and ventricular contractions.

The question tests understanding of the heart’s electrical conduction pathway and the order in which impulses travel from the SA node to the ventricles. The correct sequence starts at the SA node in the right atrium, then moves to the atrioventricular (AV) node where there is a brief delay to allow atrial contraction, then proceeds to the bundle of His (AV bundle) in the interventricular septum, then branches into the right and left bundle branches, and finally reaches the Purkinje fibers that distribute the impulse through the ventricles to coordinate contraction. This order is why this option is best: it keeps the AV node as the gateway after the SA node, follows with the His bundle, then the bundle branches, and ends with the Purkinje network.

Other sequences place Purkinje fibers too early or skip the AV node and His bundle, which would disrupt the normal flow of excitation and timing of atrial and ventricular contractions.