Heart Sounds and Valve Closure — NEET Biology
✅ Asked in NEET 2024‘Lub’ sound of heart is caused by the ________.
‘Lub’ sound of heart is caused by the ________.
Answer & NCERT explanation
Correct answer: D — Closure of the tricuspid and bicuspid valves
The 'lub' sound (S1) occurs when the AV valves (tricuspid and bicuspid) close at the beginning of ventricular systole. This prevents backflow of blood from ventricles to atria. The 'dub' sound (S2) is caused by semilunar valve closure. NCERT clearly states this sequence of heart sounds.
Read more NCERT concept on the PYQ
During each cardiac cycle two prominent sounds are produced which can be easily heard through a stethoscope. The first heart sound (lub) is associated with the closure of the tricuspid and bicuspid valves whereas the second heart sound (dub) is associated with the closure of the semilunar valves. These sounds are of clinical diagnostic significance.
The NTA tests your knowledge of which valves produce which heart sounds. The first sound (lub) comes from tricuspid and bicuspid valve closure during ventricular contraction, while the second sound (dub) comes from semilunar valve closure during ventricular relaxation. Students often confuse which valves produce which sounds or mix up the timing. Remember: lub = AV valves closing (tricuspid + bicuspid), dub = semilunar valves closing (aortic + pulmonary). These are clinically important findings that doctors detect using a stethoscope, making it a high-yield NEET topic.
What does NCERT say about During each cardiac cycle?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.