Final answer:
The electrical impulse is delayed as it passes through the AV node, allowing the atria to contract before the ventricles.
Step-by-step explanation:
The electrical impulse is delayed as it passes through the AV node, which permits the atria to contract before ventricles. The impulse spreads from the sinoatrial (SA) node through the atria and reaches the atrioventricular (AV) node. The AV node causes a delay of approximately 100 ms before transmitting the impulse to the ventricles. This delay allows the atria to complete their contraction and pump blood into the ventricles.