Rigor mortis is the stiffening of a body after death that occurs when myosin binds to actin but cannot unbind. What prevents myosin from unbinding?

Key Concepts

Muscle Contraction Mechanism

Muscle contraction occurs through the sliding filament theory, where myosin heads bind to actin filaments, forming cross-bridges. This process requires ATP, which provides the energy for myosin to pull actin and subsequently release. In rigor mortis, the lack of ATP prevents myosin from detaching from actin, leading to sustained muscle contraction and stiffness.

Role of ATP in Muscle Function

Adenosine triphosphate (ATP) is crucial for muscle function, as it supplies the energy needed for muscle contraction and relaxation. During contraction, ATP is hydrolyzed to ADP and inorganic phosphate, allowing myosin to release from actin. After death, ATP production ceases, resulting in myosin remaining bound to actin, which is a key factor in the development of rigor mortis.

Biochemical Changes Post-Mortem

After death, the body undergoes various biochemical changes, including the depletion of ATP and the accumulation of calcium ions. The lack of ATP prevents muscle fibers from relaxing, while increased calcium levels promote continued binding of myosin to actin. These changes contribute to the onset of rigor mortis, which typically begins a few hours after death and can last for several days.