Muscle Physiology and Contraction · USMLE Step 1

Which band(s) of the sarcomere shorten during contraction as thin and thick filaments slide past each other?

  1. A band only
  2. I band and H zone
  3. Z disc width
  4. M line length
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Correct answer: I band and H zone

During contraction, the I band (only thin filaments) and H zone (only thick filaments) decrease as thin filaments slide toward the center; A band remains constant.

Difficulty: Medium Question 11 of 20

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