Contraction, fiber types

Papadopoulos, S., K.D. Jurgens, and G. Gros (2000). Protein diffusion in living skeletal muscle fibers dependence on protein size, fiber type, and contraction. Biophys. J. 79 2084-2094. 

Myocardial hypertrophy The heart increases in size, and the chambers dilate. Initially, stretching of the heart muscle leads to a stronger contraction of the heart. However, excessive elongation of the fibers results in weaker contractions. This type of failure is termed systolic failure and is a result of a ventricle unable to pump effectively. Less commonly, patients with CHF may have diastolic dysfunction—a term applied when the ventricles ability to relax and accept blood is impaired by structural changes, such as hypertrophy. The thickening of the ventricular wall and subsequent decrease in ventricular volume decreases the ability of heart muscle to relax. In this case, the ventricle does not fill adequately, and the inadequacy of cardiac output is termed diastolic heart failure. 

Mammalian skeletal muscle can be separated Into two distinct fiber populations, based on relative contraction characteristics, and are referred to as slow-twltch (Type I) or fast-twitch (Type II) fibers. The slow-twltch fiber type exhibits a relatively low shortening velocity (27), a low rate of tension development (27). a low myosin ATPase activity (28) and a low rate of calcium sequestration by the sarcoplasmic reticulum (29). The converse Is true for the fast-twitch fibers. Since contraction velocity highly correlates with myosin ATPase activity (30), It Is possible to easily Identify,... 

Mackle, B. G. and Terjung, R. L. (1983) Blood flow to different skeletal muscle fiber types during contraction. Am. J. 

Rail, J. (1985) Energetic aspects of skeletal muscle contraction Implications of fiber types. Ex. Sport. Scl. Rev. Vol. 13. 

The developmental aspects of the differentiation of fiber types has been studied by a number of workers. It has become clear that at an early age all or most muscles tend to resemble more closely red muscles, both in their speed of contraction and in their metabolic pattern. Bass and coworkers (B5) have recently detailed the developmental changes in glycolytic and oxidative enzymes in red and white muscle in the chicken their results illustrate the much greater changes which occur in white muscle. 

Although the human has no muscles that consist entirely of this fiber type, many animals do. Examples are white abdominal muscles of fish and the pectoral muscle of game birds (turkey white meat). These muscles contract rapidly and vigorously (the fast twitch refers to the time to peak tension), but only for short periods. Thus, they are used for activities such as flight in birds and sprinting and weight-lifting in humans. 

EXAMPLE 13.21 Type II muscle fibers are subdivided into type Ila and type Ilb. Type Ila can use both aerobic and anaerobic metabolism to produce ATP whereas type lib fibers use only anaerobic metabolism. In contrast to type I muscle fibers, type lib fibers contract rapidly after stimulation by a nerve impulse. They have evolved for short-lived, powerful contractions by the possession of characteristically active myosin ATPases and a dense packing of contractile filaments. So much of the cytoplasmic space is taken up with filaments that little exists for mitochondria. Similarly, these fibers are associated with a relatively poor blood supply. Type lib fibers are also known as white and fast-twitch muscle fibers and are adapted for short-lived but powerful contractions. The relative paucity of mitochondria and the poor blood supply impose obvious constraints on the generation of ATP during exercise. 

A hollow-fiber-type module was developed and a fundamental patent was filed by Dow Chemical in 1960. An RO module using the cellulose triacetate hollow fiber is indicated there (Mahon, 1966). A significant portion of research and development at Dow Chemical was carried out based on its research contract with OSW, and the development results of the RO module for brackish water was published in 1970 and for seawater in 1974. The RO module using cellulose triacetate hollow fiber for brackish water was marketed in 1974 (Dance et al., 1971 Ammons and Mahon, 1974). 

Muscle tissue is unique in its ability to shorten or contract. The human body has three basic types of muscle tissue histologically classified into smooth, striated, and cardiac muscle tissues. Only the striated muscle tissue is found in all skeletal muscles. The type of cells which compose the muscle tissue are known as contractile cells. They originate from mesenchymal cells which differentiate into myoblasts. Myoblasts are embryonic cells which later differentiate into contractile fiber cells. 

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