Where does an impulse start in the heart?

The sinoatrial (SA) node is correctly identified as the starting point of an impulse in the heart. It is often referred to as the heart's natural pacemaker because it initiates the electrical impulses that trigger each heartbeat. The SA node is located in the right atrium and generates electrical signals that spread throughout the walls of the atria, causing them to contract and push blood into the ventricles.

This initial impulse set by the SA node is vital for maintaining the coordinated rhythm of the heart. After the impulse is generated, it travels to the atrioventricular (AV) node, where it is briefly delayed before moving on to the Bundle of His and then into the Purkinje fibers throughout the ventricles, which coordinate contraction of the ventricles. Understanding the role of the SA node is essential for grasping how the heart regulates its rhythm and responds to various physiological demands.