Moderate
Skeletal muscles______________?
Correct answer: C. Contraction is initiated by calcium binding to troponin
- A. Contracts when calcium is taken up by sarcoplasmic reticulum
- B. Contracts when actin and myosin filaments shorten
- C. Contraction is initiated by calcium binding to troponin
- D. Contraction is initiated by calcium binding to tropomyosin
Explanation
Calcium released from the sarcoplasmic reticulum binds to troponin C, moving tropomyosin away from actin's binding sites and initiating cross-bridge cycling. Actin and myosin filaments slide past one another rather than shortening themselves.
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