Rigor Mortis Writing Assignment: Week 11

Topics: Myosin, Actin, Protein Pages: 2 (525 words) Published: June 5, 2012
Justin Mang A&P 130
Crime scene investigators have the unique ability of seeing the unseen. This ability is not a perfect science, but they figure out what they need to through process of elimination and logic. When the investigator enters the scene and come upon a corpse time is ticking and an estimated time of death is important. Rigor Mortis gives an approximate time of death, but is it accurate enough to be used during an investigation when time is of the essence?

To make this determination we must first understand what rigor mortis is and to do that we must understand how the muscles work. To explain a muscle contraction in great detail would make this essay quite lengthy so I’ll talk about the basics needed to explain rigor mortis. In striated, voluntary skeletal muscles there are two myofilaments in the myofibrils that are the key to muscle contraction. These two myofilaments are called thick and thin filament simply enough. The thick filaments are made up of protein molecules called myosin. “A myosin molecule is shaped like a golf club, with two polypeptides intertwined to form a shaft like tail and a double globular head projecting from it at an angle” (Saladin.408). Thin filaments have three main components called actin, tropomyosin, and troponin. For a muscle to contract the myosin will bind with actin. The tropomyosin and troponin work together to cover the actin binding site, preventing the contraction. When the body wants the muscles to contract the sarcoplasmic reticulum releases calcium to the troponin, which then uncovers the actin binding sites. This connection will only break when ATP is present to release it.

This explanation of muscle contraction is so important to understanding rigor mortis because it is exactly that. “Rigor mortis is one of the recognizable signs of death that is caused by a chemical change in the muscles after death, causing the limbs of the corpse to become stiff and difficult to move or...
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