Cardiac Cycle and Valve Function — NEET Biology
✅ Asked in NEET 2022How does the heart function? Let us take a look. To begin with, all the four chambers of heart are in a relaxed state, i.e., they are in joint diastole. As the tricuspid and bicuspid valves are open, blood from the pulmonary veins and vena cava flows into the left and the right ventricle respectively through the left and right atria. The semilunar valves are closed at this stage. The SAN now generates an action potential which stimulates both the atria to undergo a simultaneous contraction – the atrial systole. This increases the flow of blood into the ventricles by about 30 per cent. The action potential is conducted to the ventricular side by the AVN and AV bundle from where the bundle of His transmits it through the entire ventricular musculature. This causes the ventricular muscles to contract, (ventricular systole), the atria undergoes relaxation (diastole), coinciding with the ventricular systole. Ventricular systole increases the ventricular pressure causing the closure of tricuspid and
NTA tests your understanding of how the cardiac cycle coordinates atrial and ventricular contractions. Students often confuse which valves are open during each phase—remember that tricuspid and bicuspid valves are open during joint diastole (atrial filling), while semilunar valves are closed. When the SAN triggers atrial systole, it increases ventricular blood flow by 30%, then ventricular systole closes the AV valves and opens semilunar valves. A common mistake is forgetting that atrial and ventricular systoles are NOT simultaneous—they occur sequentially. To ace NEET questions, memorize the valve positions at each stage and understand how the conduction system (SAN→AVN→His bundle) coordinates these contractions in the correct sequence.
Which one of the following statements is correct? [NEET 2022 Phase 1]
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.
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