Anatomy and Physiology II Practice Test

What is the primary function of the sinoatrial node in the heart?

1. It acts as a valve between the atria and ventricles

2. It initiates and regulates the heartbeat

3. It is responsible for oxygen exchange in the blood

4. It produces hormones for heart regulation

The correct answer is: It initiates and regulates the heartbeat

The primary function of the sinoatrial node, often referred to as the SA node, is to initiate and regulate the heartbeat. Located in the right atrium of the heart, the SA node serves as the natural pacemaker by generating electrical impulses that trigger each heartbeat. These impulses spread through the atria, causing them to contract and push blood into the ventricles. In this role, the SA node maintains the heart's rhythm and ensures that the heart beats at a regulated pace, typically around 60 to 100 beats per minute in a resting adult. This function is critical for maintaining effective circulation and ensuring that the body's tissues receive an adequate supply of oxygen and nutrients. Other options relate to functions of different structures in the heart or body. For example, valves between the atria and ventricles govern blood flow direction rather than initiating the heartbeat. Oxygen exchange occurs in the lungs, not within the sinoatrial node, and hormone production related to heart function is primarily carried out by other organs, such as the adrenal glands, not the SA node itself.