- A Rigor mortis is sometimes thought to be caused specifically by ongoing active protein synthesis that continues within the dying muscle cells for some time after death in general practice as frequently described in most textbook accounts
- B After death, ATP depletion prevents myosin detachment from actin; muscles stiffen. Resolution occurs after 24-48h as lysosomal proteases (cathepsins) degrade myosin, actin, and Z discs during autolysis; muscles become flaccid again
- C Rigor mortis is sometimes thought to be caused mainly by the simple gradual buildup of lactic acid accumulating within the affected muscle fibre tissue over several hours during normal conditions as generally observed in typical laboratory settings
- D Rigor mortis is sometimes thought to represent a permanent and largely irreversible state of complete muscle stiffness that rarely resolves at any point after death occurs under usual circumstances according to most researchers
Correct answer: B. After death, ATP depletion prevents myosin detachment from actin; muscles stiffen. Resolution occurs after 24-48h as lysosomal proteases (cathepsins) degrade myosin, actin, and Z discs during autolysis; muscles become flaccid again
Explanation: Rigor mortis mechanism: ATP depletion after death → myosin heads cannot detach from actin (no ATP for step 5 of cross-bridge cycle) → permanent rigor complex. Onset 2-6h (glycolysis exhausted). Resolution 24-48h: autolytic proteases (cathepsins, calpains) from lysosomes degrade myofilaments. Forensically: degree of rigor helps estimate time of death.
Concept context
Types of movement, muscle contraction, skeletal system, joints, and disorders. Important for Class 11 and NEET.