What causes the first heart sound ('lub')?
Answer and explanation
Correct answer: D. The closing of the atrioventricular valves at the start of ventricular systole
- Step 1: Ventricular pressure rises at the start of systole. Step 2. This shuts the AV valves. Answer: AV valves closing. Why not the others: these are other events in the cycle.
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More Respiration, Photosynthesis and Transport questions
- Which gas is released as a waste product of photosynthesis in plants?
- Where in the chloroplast does the light-independent reaction (Calvin cycle) take place?
- What is the first stable product of carbon fixation in the Calvin cycle?
- A plant is moved from bright light to darkness. What happens to the levels of GP and RuBP in the Calvin cycle?
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- Where does glycolysis take place and does it need oxygen?