Muscle rigor mortis

Rigor ll a muscle condition in which muscle fibers, depleted of ATP and phosphocreatine, develop a state of extreme rigidity and cannot be easily extended. (In death, this state is called rigor mortis, the rigor of death.) From what you have learned about muscle contraction, explain the state of rigor in molecular terms. 

In the absence of ATP, myosin crossbridges are unable to release the actin. As a result, the sarcomeres, and therefore the muscle, remain contracted. This phenomenon is referred to as rigor mortis. Following death, the concentration of intracellular calcium increases. This calcium allows the... 

Tenderness. The contractile state of the muscle after rigor mortis is a major factor in meat tenderness, which is affected by post-mortem conditions creating differences in tenderness. Ageing of fresh pork can be used to improve tenderness. The process is based on a continuous weakening of the structural elements by different endogenous muscle peptidases along with an improved palatability (Taylor et al., 1995). 

Postmortem examination in fatal cases has shown immediate onset of extreme rigor mortis in the muscles of the thighs and legs, edema and intraalveolar hemorrhage in the lungs, cerebral edema, and liver and kidney damage. The risk of serious intoxication is increased during hot weather. ... 

How We Become a Stiff When a higher vertebrate dies, its muscles stiffen as they are deprived of ATP, a state called rigor mortis. Explain the molecular basis of the rigor state. 

The biochemical state of the muscle, i.e., interactions of the proteins of the myofibril (e.g., in rigor mortis, cold shortening, and thaw rigor), as well as the proteolytic changes during aging of the meat... 

Before the influence of freezing was studied, it was necessary to determine whether postmortem (p.m.) storage of muscle at temperatures above freezing (+4°C) influenced the subcellular distribution of the enzymes investigated. As is well known, storage of muscle p.m. results in drastic changes such as development of rigor mortis and a decline in pH from above 7 to about 5.5. 

Muscular tissue, after death or continued contractions, contains the mixture of acids known to the older authors as sarcolactid acid. Normal, quiescent muscle is neutral in reaction but, when rigor mortis appears, or if the muscle be tetanized, its reaction becomes acid from the liberation of BArcolactic acid. Whether these acids are formed de nooo during the contraction of the muscle, or whether they are produced by the decom-... 

The extent of shortening that a muscle, free to shorten, undergoes as rigor mortis develops is a direct function of the temperature down to about 14°-19°C (31). Below 14°C there is an increasing tendency for this muscle to shorten further. This cold-shortening phenomenon is associated with very tough meat upon cooking. Rhodes and Dransfield... 

Stanley (1983) concluded that postmortem events influence the physical properties of meat, not only through rigor mortis, but also as a result of the action of numerous endogenous enzymes on myofibrillar structure, and perhaps, connective tissue as well. A major structural alteration that has been observed in postmortem muscle is Z-disc degradation. The unreactive chemical nature of collagen may preclude any major attack by endogenous muscle enzymes on this fibrous protein (Offer et al, 1988). 

Rigor mortis is the stiffening of the muscles that occurs shortly after death. Since very little or no ATP is present, muscles are left contracted, stiff, and unable to relax. 

Rigor Mortis, The Stiffening of a Dead Body, Accompanying the Depletion of Adenosine Triphosphate in the Muscle Fibers ... 

Low field NMR has become a valuable tool in the research of muscle structure of meat and fish and has given valuable information about the water behaviour in such biological systems. The aim of this paper was to study the differences in farmed and wild cod muscle as indicated by low field relaxation measurements and how these results can be related to more traditional measurements of physical, chemical and sensory analysis and how different processing, such as filleting pre or post rigor mortis, salting and superchilling affected these parameters. 

---