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Download MUSCULAR SYSTEM - Simon Land
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MUSCULAR SYSTEM Chapter 7 Muscular System ½ our body weight comes from muscle tissue. Over 656 different muscles in the human body. Responsible for all body movement. Give our body form and shape. Functions: 1. 2. 3. Body movement Body form and shape, to maintain posture Body heat, to maintain body temperature. TYPES OF MUSCLES Skeletal muscles - striated Smooth muscle – spindle-shaped Cardiac muscle – non-striated Sphincter (dilator) muscles TYPES OF MUSCLES Skeletal Attached to bone and skeleton Are called striped or striated b/c have cross bandings of alternating light and dark band running perpendicular to the length of the muscle. Voluntary muscle Skeletal Muscle Muscle cells Multinucleate Cell – muscle fiber Cell membrane – sarcolemma Cytoplasm – sarcoplasm Contract quickly, fatigue easily, lack ability to remain contracted. Smooth muscle Cells Small and spindle-shaped Only one nucleus, located at the center of the cell Are unmarked by any distinctive striations Unattached to bones, act slowly, do not tire easily, can remain contracted for a long time. Smooth muscle Not under conscious control Called involuntary muscles Controlled by the autonomic nervous system Found in the walls of the internal organs Help push food along the alimentary canal, contract during labor, control the diameter of blood vessels. Cardiac muscle Found only in the heart Cells Are striated and branched Involuntary Joined in a continuous network w/o a sheath separation Membranes are fused at places called intercalated discs. Cardiac muscle When one cell receives a signal to contract, all neighboring cells are stimulated and they contract together to produce a heart beat. Requires a continuous supply of oxygen to function. If cut off for as little as 30 seconds, the muscle cells start to die. Sphincter, dilator muscle Special, circular muscles in the openings b/w the esophagus and stomach, and the stomach and small intestine. Also in walls of anus, urethra, and mouth. They open and close to control the passage of substances.
