When an electrical impulse reaches the atrioventricular node, what is the purpose of its brief delay?

The brief delay that occurs when an electrical impulse reaches the atrioventricular (AV) node serves a crucial purpose in the cardiac cycle. This delay allows for adequate ventricular filling before the ventricles contract.

When the electrical impulse moves from the atria to the ventricles, a coordinated sequence of events is necessary for effective heart function. The atria contract first, pushing blood into the ventricles. The delay at the AV node ensures that the atria have enough time to fully empty their contents into the ventricles before the ventricles begin to contract. This timing is essential for maintaining optimal stroke volume and ensuring that the heart pumps efficiently.

If the impulse were to pass through the AV node too quickly, the ventricles would begin contracting before they are adequately filled with blood, potentially leading to reduced cardiac output and compromised circulation. Thus, the delay at the AV node is a critical physiological mechanism that supports effective heart function by facilitating proper ventricular filling.