Family Nurse Practitioner Exam

What change occurs with the S1 heart sound during auscultation?

1. Opening of the semilunar valves

2. Closure of the atrioventricular valves

3. Closure of the aortic valves

4. Opening of the atrioventricular valves

The correct answer is: Closure of the atrioventricular valves

The S1 heart sound, often referred to as the "lub" sound, is produced primarily by the closure of the atrioventricular (AV) valves, which include the tricuspid and mitral valves. This sound occurs at the beginning of ventricular contraction (systole), marking the transition from diastole to systole. When the ventricles fill with blood during diastole, the pressure rises as they contract, causing the AV valves to close to prevent the backflow of blood into the atria. The sharp closure of these valves generates the S1 sound that can be auscultated with a stethoscope. The other options relate to different cardiac activities: the opening of the semilunar valves corresponds with the S2 heart sound, while the closure of the aortic valves and the opening of the atrioventricular valves do not directly correlate with the sound produced during the S1 phase. Therefore, understanding that S1 is specifically associated with the closure of the AV valves reinforces why that choice is correct.