Question

Where is the main delay in the conduction pathway of the heart, responsible for slowing down the impulse and allowing the atria to contract before the ventricles?

a) Atrioventricular (AV) node

b) Sinoatrial (SA) node

c) Bundle of His

d) Purkinje fibers

Answer 1

The main delay in the heart's conduction pathway occurs at the atrioventricular (AV) node, allowing the atria to contract before the ventricles.

Step-by-step explanation:

The main delay in the conduction pathway of the heart, which is responsible for allowing the atria to contract fully before the ventricles, occurs at the atrioventricular (AV) node. The AV node provides a critical pause of approximately 100 ms (milliseconds) in the electrical conduction system of the heart. This delay ensures that the atria can complete their contraction and pump blood into the ventricles before the ventricles begin to contract. The AV node's smaller cell diameter and less efficient conduction between nodal cells contribute to this delay. Extreme stimulation can cause the AV node to transmit impulses at a maximum rate of 220 per minute, establishing the healthy young adult's maximum heart rate.