Final answer:
Rigor mortis is the post-mortem stiffening of muscles, beginning within 2 to 6 hours of death and peaking around 12 hours. It results from the binding of myosin to actin filaments due to the lack of ATP. Variables such as temperature can affect the rigor mortis timeline.
Step-by-step explanation:
Rigor mortis, a condition that affects the body after death, involves the stiffening of muscles due to biochemical changes within muscle tissue. When a person is alive, muscle contraction and relaxation are facilitated by the interaction of myosin and actin within muscle cells, using energy from adenosine triphosphate (ATP). After death, ATP is no longer produced, which disrupts the cycle of muscle contraction and causes myosin heads to remain bound to actin filaments. This results in muscle stiffness characteristic of rigor mortis.
Rigor mortis onset varies but typically begins within 2 to 6 hours post-mortem and reaches its maximum stiffness after 12 hours. The condition then gradually dissipates over the following 48 to 60 hours. Variables such as ambient temperature and the physical condition of the body at the time of death can affect the timeline.
Contrary to popular belief, rigor mortis is not a condition that affects living individuals. When myosin heads detach rapidly from the actin-binding sites in a living person, it can result in conditions such as "writer's cramp" due to temporary muscle fatigue, not rigor mortis.