The given diagram shows the ultra-structure of a sarcomere.The muscle in this diagram is in relaxed form because in its sarcomere
Correct answer: C. H zone is visible
- A. I band is short
- B. A band is short
- C. H zone is visible
- D. Z lines are visible
Explanation
The H zone is visible when the muscle is relaxed and becomes less visible or disappears during contraction. So option C is correct.The I band shortens during muscle contraction, so A is incorrect. The A band remains constant in length during both contraction and relaxation, so B is incorrect. Z lines are always visible in a sarcomere, so D is incorrect.
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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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