Final answer:
The sinoatrial (SA) node functions as the heart's natural pacemaker, initiating electrical impulses that lead to the coordinated contraction of the heart's atria and ventricles.
Step-by-step explanation:
The function of the sinoatrial (SA) node is to serve as the natural pacemaker of the heart. It is responsible for initiating the electrical impulses that set the rhythm for the contraction of the heart, specifically by producing an electrical impulse that causes the two atria to contract. The SA node, located in the right atrium, has the highest rate of depolarization within the heart's conduction system. Once the SA node generates an action potential, it spreads across the atria, causing them to contract and pushing blood into the ventricles. This impulse then reaches the atrioventricular (AV) node, where it briefly pauses before continuing to the ventricular myocardium, resulting in ventricular contraction.
This process ensures that the heart beats in a coordinated manner, with the atria contracting slightly before the ventricles, allowing for efficient blood flow. The electrochemical activity of the SA node and the cardiac conduction system as a whole can be measured by an electrocardiogram (ECG), which tracks the electrical impulses of the cardiac muscle.