Arizona State University (ASU) BIO202 Human Anatomy and Physiology II Exam 1 Practice Exam

The cardiac conduction system starts at the sinoatrial (SA) node, which is often referred to as the natural pacemaker of the heart. This specialized group of cells is located in the right atrium and is responsible for initiating the electrical impulses that set the rhythm for the entire heart. The SA node generates action potentials that propagate through the atria, causing them to contract and push blood into the ventricles.

Once the impulse is generated by the SA node, it travels to the atrioventricular (AV) node, which serves as a relay point before the signal moves on to the ventricles. However, the process begins specifically with the SA node, as it is the first structure in the conduction pathway. The Bundle of His and Purkinje fibers are part of this pathway that helps conduct impulses through the ventricles, but they do not initiate the conduction process. Thus, the SA node is critical in maintaining the heart's rhythm and ensuring that it beats in a coordinated manner.