What is the second internal pacemaker after the signal travels through the atria?

The second internal pacemaker in the heart, after the electrical signal has traveled through the atria, is the atrioventricular (AV) node. The AV node serves as a crucial relay point in the cardiac conduction system, receiving the electrical impulse from the sinoatrial (SA) node, which is located in the right atrium and initiates the heartbeat.

Once the impulse reaches the AV node, it has the essential role of delaying the signal slightly before it moves on to the ventricles. This delay allows the atria to finish contracting and fully emptying their blood into the ventricles before the ventricles begin their contraction. This coordinated contraction is vital for effective blood pumping throughout the body.

After the AV node, the signal is conducted to the Bundle of His, then to the Purkinje fibers, which ultimately trigger ventricular contraction. However, the immediate role of the AV node as the second pacemaker is critical in ensuring proper timing in the heart's electrical activity and overall function.