Muscle Characteristics

The four special functional characteristics of muscle that are the basis for muscle response are contractility, excitability, extensibility, and elasticity (Muscle, 2004). Contractility allows a muscle to shorten with force, to lengthen passively, and to move. Excitability allows a muscle to respond to a stimulus, and to maintain chemical potentials across its cell membranes. Extensibility allows a muscle to be stretched, repeatedly and considerably, as needed, without being damaged. Elasticity allows a muscle to return to its normal length after being stretched or shortened.

2. Distinguish between (a) direct and indirect muscle attachments, and (b) a tendon and an aponeurosis.

Every one of the body's muscles is attached to bone or other connective tissue structures at a minimum of two points, and the point where the muscle is attached to an immovable bone is called the origin, and the point where it is attached to a moveable bone or tissue is called the insertion (Skeletal, 2004). When a muscle contracts, the moveable bone or tissue always moves towards the immovable bone, i.e. the insertion moves towards the origin.

Muscles attach to bones directly by extensions of the muscle fascia if the attachments are broad, such as in the diaphragm and the scapulae (Skeletal, 2004). Other muscles attach indirectly to bones through tendons, which are fibr

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ime, so the contractile response can be graded. 5. Describe the three distinct types of skeletal muscle fibers. There are three types of skeletal muscle fibers which differ in their diameter and in their color (Ross, Romrell and Kaye, 1995, 215-216). These fiber types can be distinguished by observing fresh muscle tissue, and by staining fixed samples of tissue histochemically for oxidative enzyme activity. The three types of fibers are red fibers, white fibers, and intermediate fibers. The red fibers are small fibers, and they have large amounts of myoglobulins and cytochromes and many mitochondria in their cytoplasm. The white fibers are large muscle fibers, and have less myoglobin and cytochromes, and have fewer mitochondria in the cytoplasm. The intermediate fibers are of intermediate size, and have pigment contents and mitochondrial numbers somewhere between those of the red fibers and the white fibers. Myoglobin is the oxygen-carrying pigment, something like hemoglobin, found in muscle cells. Red fibers make up slow-twitch motor units and have a great resistance to fatigue (Ross, Romrell and Kaye, 1995, 224). Myosin ATPase activity is the highest in red muscle fibers. Red muscle fibers are found most often i
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