Question: When is the second sound of the heartbeat produced?

context: The second heart sound, or S, forms the "dub" of "lub-dub" and is composed of components A (aortic valve closure) and P (pulmonary valve closure). Normally A precedes P especially during inspiration where a split of S can be heard. It is caused by the closure of the semilunar valves (the aortic valve and pulmonary valve) at the end of ventricular systole and the beginning of ventricular diastole. As the left ventricle empties, its pressure falls below the pressure in the aorta. Aortic blood flow quickly reverses back toward the left ventricle, catching the pocket-like cusps of the aortic valve, and is stopped by aortic valve closure. Similarly, as the pressure in the right ventricle falls below the pressure in the pulmonary artery, the pulmonary valve closes. The S sound results from reverberation within the blood associated with the sudden block of flow reversal.
question: What is typically the earlier component of the second sound of the heartbeat?
short_answers: aortic valve closure
A2
context: The second heart sound, or S, forms the "dub" of "lub-dub" and is composed of components A (aortic valve closure) and P (pulmonary valve closure). Normally A precedes P especially during inspiration where a split of S can be heard. It is caused by the closure of the semilunar valves (the aortic valve and pulmonary valve) at the end of ventricular systole and the beginning of ventricular diastole. As the left ventricle empties, its pressure falls below the pressure in the aorta. Aortic blood flow quickly reverses back toward the left ventricle, catching the pocket-like cusps of the aortic valve, and is stopped by aortic valve closure. Similarly, as the pressure in the right ventricle falls below the pressure in the pulmonary artery, the pulmonary valve closes. The S sound results from reverberation within the blood associated with the sudden block of flow reversal.
question: What is typically the later component of the second sound of the heartbeat?
short_answers: P2
pulmonary valve closure
context: No context provided
question: What acoustical phenomenon within blood is associated with the second sound of the heartbeat?
short_answers: reverberation
reverb

Answer: The second heart sound follows the first, but the cause of each is different. The first heart sound occurs when the atrioventricular valves close at the beginning of ventricular contraction, or systole, while the second heart sound occurs when the aortic valve and pulmonary valve close at the end of ventricular systole and the beginning of ventricular diastole. The second heart sound consists of aortic valve closure followed by pulmonary valve closure and is also associated with the acoustical phenomenon within blood called reverberation.