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Muscle, tissue or organ of the body characterized by the ability to contract, usually in response to a stimulus from the nervous system. The basic unit of all muscle is the myofibril, a minute, threadlike structure composed of complex proteins. Each muscle cell, ....

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.... muscle because it can be consciously controlled through the central nervous system. Smooth muscle is the muscle of the internal organs and is called involuntary because it is not under voluntary control. Cardiac muscle is a special type of muscle found only in the heart. It consists of linked fibers that contract in unison producing the heartbeat. Skeletal, or Striated Muscle Tissue: This type of muscle is composed of long fibers surrounded by a membranous sheath, the sarcolemma. The fibers are elongated, sausage-shaped cells containing many nuclei and clearly display longitudinal and cross striations. Skeletal muscle is supplied with nerve ....