Patient Care Technician (PCT) AAH Practice Exam

What does the SA node influence in the cardiovascular system?

1. Blood circulation

2. Heart rate

3. Blood pressure

4. Vascular resistance

The correct answer is: Heart rate

The SA node, or sinoatrial node, is often referred to as the natural pacemaker of the heart. Its primary function is to generate electrical impulses that initiate each heartbeat. This activity directly influences the heart rate by determining how quickly the heart contracts and pumps blood throughout the body. When the SA node fires an impulse, it spreads through the heart, leading to coordinated contractions of the heart chambers, specifically the atria and ventricles. The other options relate to aspects of the cardiovascular system but are not directly controlled by the SA node. Blood circulation is influenced by multiple factors, including heart rate and blood vessel health, but is not a direct function of the SA node itself. Blood pressure is dependent on the volume of blood being pumped and the resistance offered by the arterial walls; while heart rate (influenced by the SA node) can affect blood pressure, the SA node does not regulate blood pressure directly. Vascular resistance pertains to the constriction or dilation of blood vessels, which is controlled by smooth muscle activity and other mechanisms within the circulatory system, rather than the electrical impulses originating from the SA node.