Muscle hierarchy

As with many enzymes the role of AMP aminohydrolase in the hierarchy of metabolic catalysts is not clearly understood. Enzymic activity in muscle is markedly reduced in the dystrophic mouse (161, 162), in humans suffering from Duchanne type muscular dystrophy (163), in hypokaliemic periodic paralysis (164), and upon denervation of normal and dystrophic mouse gastronemii (165). Activity is reported to increase in both transplanted and primary hepatomas (151) and in precancerous livers prior to the onset of neoplasia induced by feeding or by intraabdominal injections of the potent carcinogen 3 -methyl-4-dimethyl-aminoazobenzene (166). The weak carcinogen, 4 -methyl-4-dimethyl-aminoazobenzene was not effective (166). Increases in enzyme activity concomitant with altered nuclear-nucleolar morphology, nuclear RNA content, and nuclear RNA biosynthesis were also observed after injections of thioacetamide, a hepatocarcinogen (167, 168). 

The hierarchy of muscle organization. A voluntary muscle such as the bicep is a composite of many fibers connected to tendons at both ends. Each muscle fiber is composed of several myofibrils that are surrounded by an electrically excitable membrane (sarcolemma). 

On the Friday night before a Sunday show, the athlete stops water intake. The body thinks it will still get the 1.5-2.0 gallons of water daily and continues to excrete water at its normal rate. This causes a decrease in blood volume and of course muscle water volume. Remember the body s water hierarchy Well, as a survival response or reaction, the body gives up water from the area of least importance as a means of compensation. Yup, you got it. Subcutaneous water is pumped into blood and muscles. The result is vascularity, full muscle bellies, and paper thin skin. 

Fig. 1. (A) Schematic illustration of the hierarchy of muscle. Skeletal muscle is...

The different fuels used by exercising muscle are discussed in subsequent sections. These fuels may be arranged in the following "hierarchy," where the order of appearance approximates relative importance during exercise (1) creatine phosphate, (2) muscle and liver glycogen, (3) gluconeogenesis, and (4) fatty acids. 

The body s stores of glycogen may be depleted by about an hour of stnenuous exercise. Therefore, glycogen is listed after creatinine phosphate in the hierarchy of energy fuels, A "typical 70 kg man" contains about 350 g of muscle glycogen, 30 g of liver glycogen, and 20 g of glucose in extracellular fluids. 

The penalty to be paid for antagonistic control action is energy inefQciency. Maintaining active control in both directions means that both sets of muscles will, at least in part, be working against each other. This wastes energy (see Section 6.14), but in the hierarchy of priorities, loss of control is more wasteful. 

Related to the idea of hierarchy is the use of modular stmeture building up materials through the assembly of identical smaller units. The stepwise unfolding of the muscle protein titin is due to a kind of modular domain stmeture and gives it a sawtooth stress—strain curve, very dilTerent from a purely elastic filament. Similar force curves were measured for the polymeric filaments that are pulled out from the organic binder between the aragonite plates of nacre as the plates are separated (Fig. This... 

The muscular contraction implies the most important, most versatile as performances motility mechanism in the living life, and practically the only one able of evolutionary perfecting. Its support, the skeletal muscle, presents a complex structure, having at list six levels of hierarchy, Figure 4.2. 

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