rigor mortis notes draft

Rigor mortis is the chemical change in one’s body after death characterized by the stiffness and rigidity of the limbs. Rigor mortis is caused by the lack of ATP in the body after the organs shut down. ATP is needed for muscle contraction as it binds to myosin and allows myosin to pull the thin filaments of the muscle closer to the sarcomere. However, once the ATP is used up, the contracted muscles cannot relax because ATP is required for the myosin to release from the actin binding site and reset itself. Therefore, when the ATP runs out, the muscles stay in a contracted state causing stiffness. Rigor mortis is the third stage of death and can last up to eighteen hours. However, the rigor goes away after some time because the proteins completely denature. The proteins denature because the calcium is eventually pumped away from the troponin binding sites, allowing them to cover up the actin binding sites. Once the actin binding sites are covered up, the myosin can detach and relax the muscle.