Postmortem spasm

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Sometimes, after an organism has died, small movements of the limbs (a twitch of a finger or even a whole leg moving) can be observed. This phenomenon, known as postmortem spasm, can be observed in human cadavers as well as smaller organisms that have died, as rigor mortis sets in.

ATP is required to reuptake calcium into the sarcomere's sarcoplasmic reticulum (SR). When a muscle is relaxed, the myosin heads are returned to their "high energy" position, ready and waiting for a binding site on the actin filament to become available. Because there is no ATP available, previously released calcium ions cannot return to the SR. These leftover calcium ions move around inside the sarcomere and may eventually find their way to a binding site on the thin filament's regulatory protein. Since the myosin head is already ready to bind, no additional ATP expenditure is required and the sarcomere contracts. When this process occurs on a larger scale, the disturbing twitches and gruesome postures associated with rigor mortis can occur.

[edit] See also

• Cadaveric spasm
• Galvanism
• Postmortem movement
• Rigor Mortis

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