Asked in PMC Practice Test 33 (2021) 2021Moderate

How many actin filaments surround each myosin filament?

Correct answer: C. 6

  • A. 2
  • B. 4
  • C. 6
  • D. 8

Explanation

The myosin filament is surrounded by six actin filaments and each actin filament is in turn surrounded by three myosin filaments. This arrangement of the actin and myosin filaments produces a striated appearance to the muscle. (Fact) The other options are 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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