Final answer:
The AV node ensures a critical delay in the cardiac conduction system to allow the atria to contract and pump blood into the ventricles efficiently before the ventricles receive the impulse, with a maximum conduction rate of 220 impulses per minute in young healthy individuals.
Step-by-step explanation:
Understanding the Atrioventricular (AV) Node:
The AV node is a crucial component of the cardiac conduction system, playing a pivotal role in heart function. When an electrical impulse originates from the sinoatrial (SA) node, it spreads through the atria and reaches the AV node. An interesting characteristic of the AV node is the intentional delay before depolarization and transmission of the impulse to the atrioventricular bundle. This delay, lasting approximately 100 milliseconds (ms), is due to the small diameter of the nodal cells, which slows the impulse, and the less efficient conduction between these cells. This pause is essential as it allows the atria to complete their contraction, effectively pumping blood into the ventricles before the ventricular myocardium is activated. In cases of extreme stimulation, the AV node can transmit up to 220 impulses per minute, which sets the maximum heart rate for a healthy young individual. The AV node can independently initiate contractions at a rate of 40-60 beats per minute if the SA node fails, sufficient to sustain consciousness.