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Unformatted text preview: Chapter 10: The Muscular System--Introduction Chapter Overview Skeletal muscle is the most abundant tissue in the body. Along with bones, it provides the basis for movement, and is central to the health and activity of an individual. The term muscular system refers only to skeletal muscle but cardiac and smooth muscle are also briefly discussed in the chapter. Muscle Types and Functions Skeletal Muscle Skeletal muscle consists of striated cell called muscle fibers or myofibers. Striations give the muscle a striped appearance under the microscope, and are the result of overlapping arrangement of proteins. Skeletal muscle produces voluntary movement by attaching to bone. It is sometimes called voluntary muscle because it is subject to conscious control. Cardiac Muscle Cardiac muscle is found in the walls of the heart, and is responsible for its contraction. Like skeletal muscle, cardiac muscle is striated, but it is involuntary. The cells are called myocytes, cardiomyocytes, or cardiocytes. Smooth Muscle Contractile proteins are not arranged in the same way as in other muscle types, and there are no striations. The cells are called myocytes and they are short and fusiform. Smooth muscle is involuntary. Functions of Muscle 1. Movement is an obvious function of muscle. Skeletal muscle underlies our ability to transport ourselves by walking bipedally and to perform actions that range from rolling our eyeballs to picking up a pencil. Communication depends on facial expressions, speech, and writing (or typing on a computer). All these actions are possible because of movement of skeletal muscles. Contraction of smooth and cardiac muscle underlies movement of organs that support digestion and circulation. 2. A second function is that skeletal muscles maintain stability by resisting the pull of gravity so we do not fall over, and by holding bones in place. 3. Control of body openings and passages is a role of muscle. Sphincter muscles in the eyelids, pupil, and mouth control admission of light, food, and drink. Other sphincters control elimination of waste from the urethra and anus, and the movement of bile, food, and other materials through tubes in the body. 4. As much as 85% of body heat is produced by skeletal muscle. 64 5. Muscle plays a role in glycemic control , regulation of blood sugar. A lower skeletal muscle mass is associated with increased risk of type 2 diabetes mellitus....
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This note was uploaded on 02/09/2012 for the course BIO 102 taught by Professor William during the Spring '11 term at Harvard.
- Spring '11