Which event does not occur during muscle contraction:
Correct answer: B. A-band shortens
- A. I-band shorten
- B. A-band shortens
- C. H-zone disappear
- D. Z-lines move closer
Explanation
Among the given options, the event that does not occur during muscle contraction is b) A-band shortens. The A-band remains relatively constant in length as the myosin filaments slide past the actin filaments.
This question appeared on the NUMS 2022 paper, which you can sit online with every answer explained.
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About Muscle Contraction
Muscle contraction is explained by the sliding filament model, in which myosin heads pull actin filaments within sarcomeres using ATP. The topic covers calcium, troponin, tropomyosin, the neuromuscular junction and relaxation, with attention to how filament length stays almost constant while the sarcomere shortens.
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