Muscle Contraction · Histology

Rigor mortis occurs after death because:

  1. Calcium stores are completely exhausted.
  2. The muscle fibers are physically frozen by cold temperatures.
  3. ATP is no longer available to break the cross-bridges.
  4. Proteolytic enzymes destroy the thin filaments.
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Correct answer: ATP is no longer available to break the cross-bridges.

After death, ATP production ceases. Without ATP to bind to the myosin heads, they remain permanently locked in the cross-bridge state with actin, resulting in the characteristic stiffness of the body.

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