Biochemical changes after death produce a stiffening of the muscles known as?

• A. Rigor Mortis
• B. Algor Mortis
• C. Livor Mortis
• D. Pathologist

Answer: (A)

Rigor mortis is the stiffening of the muscles that happens after death. When the heart stops, circulation ends and cells run out of oxygen, forcing a shift to anaerobic metabolism. ATP is no longer produced, and calcium builds up in muscle cells. Without ATP, the myosin heads cannot detach from actin filaments, so cross-bridges remain locked in place, causing muscles to stiffen. The onset typically begins a few hours after death, progresses to a peak, and then gradually dissipates as enzymes break down the muscle tissue and autolysis proceeds. Temperature affects the rate: warmer conditions speed onset and peak, cooler conditions slow them. This is distinct from algor mortis (body cooling) and livor mortis (blood settling), and from terms referring to professionals like a pathologist.