What do the Purkinje fibers primarily do in the heart?

The Purkinje fibers play a crucial role in the heart’s electrical conduction system, specifically in the process of ventricular contraction. They are specialized fibers that distribute electrical impulses throughout the ventricles, ensuring that the muscle cells contract in a coordinated manner. When the electrical impulses reach the Purkinje fibers, they distribute the signal rapidly to the ventricular myocardium, prompting the ventricles to contract effectively. This synchronized contraction is essential for the proper pumping of blood from the heart to the lungs and the rest of the body.

While the other options mention processes related to the heart's electrical conduction system, they do not accurately describe the primary function of the Purkinje fibers. For instance, stimulating the SA node is not their role; instead, the SA node is the heart's natural pacemaker that initiates the electrical impulses. Conducting impulses from the atria to the AV node and regulating the heart's electrical impulses are functions associated with other components of the cardiac conduction system, such as the atrioventricular (AV) node and the atrial tissue. Thus, the role of the Purkinje fibers specifically involves triggering contraction in the ventricles, making the identification of their primary function as sending impulses through the ventricles accurate.