The fundamental biochemical event responsible for the development of rigor mortis is:

• A Depletion of ATP preventing detachment of myosin from actin ✓
• B Accumulation of lactic acid causing muscle fibre contracture
• C Influx of extracellular calcium through damaged sarcolemma alone
• D Denaturation of actomyosin by rising body temperature

Explanation

After death, ATP synthesis ceases while residual ATP is consumed. Cross-bridge cycling requires ATP to detach myosin heads from actin; once ATP falls below a critical level, the actin-myosin complex remains locked and the muscle becomes rigid. Calcium also leaks from the sarcoplasmic reticulum and triggers bridge formation, but the defining event is failure of ATP-dependent detachment. Lactic acid accumulation contributes to the passage of rigor later, and denaturation of protein is the basis of heat stiffening, not ordinary rigor mortis.

Reference: The Essentials of Forensic Medicine and Toxicology, Narayan Reddy, 34th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.