Gracias por responder. The correct answer is C. Two types of skeletal muscle fibers can be found in most human muscle tissues. These are called slow twitch, or type I fibers, and fast twitch, or type II fibers, and they differ in their anatomic structure, biochemistry, and physiologic functions. Although to some extent the proportion of these teo fiber types is determined by genetics, the proportions can be altered by training. Physiologically speaking, type I fibers are designed for endurance while type II fibers are designed to promote a fast response. Therefor, individuals training for long-distance running will develop a greater number of type I fibers, while persons training for sprints will develop a greater number of fast-responding type II fibers. Greater endurance implies resistance to fatigue, and resistance to fatigue requires a dependable supply of ATP. Oxidative phosphorylation is the most efficient way to produce ATP, and as a consequence, type I fibers are designed to obtain the maximum amount of energy from oxidative phosphorylation. Thus, these fibers are particularly rich in mitochondria, the organelle in which oxidative phosphorylation occus, and they also have a high level of myoglobin, which serves as an oxygen reservoir, supplying oxygen when a sufficient quantity cannot be obtained via the circulatory system. This myoglobin tints these fibers a deep red color. Type II fibers, which fatigue more readily, do not have much myoglobin, and thus these make up white muscle. The relationship between muscle color and exercise can be observed most dramatically in fow.. Most of the dark meat is found in the legs of domestic fowl that dont fly, whereas the breast is the major source of dark meat obtained from fowl that fly a lot, such as a wild duck.
Posted on: Mon, 03 Nov 2014 15:20:32 +0000
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