What happens during muscle contraction to the length of each myosin and action filament?
Correct answer: A. Z- lines get closer
- A. Z- lines get closer
- B. A band becomes short
- C. 1 band elongates
- D. There is no change in sarcomere
Explanation
During contraction, actin slides over myosin without either filament changing length, bringing the two Z-lines closer together. Students may choose A band becomes short, but the A band represents the length of thick filaments and remains constant; the I band and H zone shorten.
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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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