Muscle Physiology and Contraction · USMLE Step 1

Which zone or band of the sarcomere remains constant in length during contraction, according to the sliding filament model?

  1. I band
  2. H zone
  3. A band
  4. Distance between Z-discs
Show answer and explanation

Correct answer: A band

The A band — the region containing the full length of the thick filaments — remains constant during contraction; shortening is due to movement of thin filaments past thick ones.

Difficulty: Medium Question 3 of 20

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