Structure of Skeletal Muscle

Structure of Skeletal Muscle - Along the length of the...

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Structure of Skeletal Muscle A muscle fiber (cell) has special  terminology and distinguishing  characteristics: class="bullet"> •   The  sarcolemma,  or plasma  membrane of the muscle cell, is highly  invaginated by transverse tubules (T  tubes) that permeate the cell. •   The sarcoplasm, or cytoplasm of the  muscle cell, contains calcium-storing  sarcoplasmic reticulum, the specialized  endoplasmic reticulum of a muscle cell.
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•   Striated muscle cells are  multinucleated. The nuclei lie along the  periphery of the cell, forming swellings  visible through the sarcolemma. •   Nearly the entire volume of the cell  is filled with numerous long myofibrils.  Myofibrils consist of two types of  filaments, shown in Figure 1: Thin filaments consist of two  strands of the globular protein  actin arranged in a double helix. 
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Unformatted text preview: Along the length of the helix are troponin and tropomyosin molecules that cover special binding sites on the actin. Thick filaments consist of groups of the filamentous protein myosin. Each myosin filament forms a protruding head at one end. An array of myosin filaments possesses protruding heads at numerous positions at both ends. Figure 1. Two types of filaments. Within a myofibril, actin and myosin filaments are parallel and arranged side by side. The overlapping filaments produce a repeating pattern that gives skeletal muscle its striated appearance. Each repeating unit of the pattern, called a sarcomere, is separated by a border, or Z disc (Z line), to which the actin filaments are attached. The myosin filaments, with their protruding heads, float between the actin, unattached to the Z disc....
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Structure of Skeletal Muscle - Along the length of the...

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