What follows the firing of the SA Node in the conduction system of the heart?

The firing of the SA Node, or sinoatrial node, initiates the electrical impulse that triggers the heartbeat. Following the activation of the SA Node, the impulse first spreads throughout the atrial myocardium. This results in atrial contraction or systole, allowing blood to flow from the atria into the ventricles.

This process is essential for effective heart function, as it ensures that the atria contract in synchrony to fill the ventricles with blood before they contract. The subsequent steps in the conduction system involve the signal moving to the atrioventricular (AV) node, then to the AV bundle (Bundle of His), and subsequently to the ventricles, but these occur after the initial activation of the atrial myocardium. Therefore, understanding the sequence of events following the SA Node's firing highlights the critical role the atrial myocardium plays immediately after the initiation of the cardiac cycle.