What is the effect of a deficit in ATP availability (e.g., ischemia) on muscle contraction and relaxation?
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Correct answer: Contraction occurs but relaxation is impaired
Without ATP, myosin heads cannot detach from actin, so cross-bridges stay locked, producing sustained contraction (rigor) and impaired relaxation; relaxation requires ATP for cross-bridge detachment and Ca²⁺ reuptake.
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