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Unformatted text preview: Lecture notes on the Muscular System Overview The body contains 3 types of muscle tissue. The differences in these types of muscle are due to their microscopic structure, their location in the body and their function and how their functions are controlled: either voluntary or involuntary (autonomic). A) Skeletal muscles- attach to the skeleton are are responsible for voluntary body movements. The fibers are multi-nucleated and transversely striated and are grouped in parallel bundles called fasiculi. The skeletal muscles are the only voluntary muscles in the body. B) Smooth muscles- occur mainly in blood vessels and tubular organs of the GI tract, reproductive, urinary and respiratory systems. These muscles are under autonomic control- they are involuntary. The muscle fibers are unstriated and contain a single nucleus. C) Cardiac muscle- is found only in the wall of the heart and has the unique property of auto-rythmicity. Its contractions are involuntary and have an intrinsic rhythm . No external stimuli is needed to make it contract. It has intercalated discs that help hold adjacent cells together and transmit the force of contraction from cell to cell. It is also striated. Skeletal Muscle System When referring to the muscular system , we are referring to skeletal muscle only. The body has more than 600 skeletal muscles. Technically speaking , each one of these muscles is an organ- it is composed of muscle tissue, nerve and connective tissue 1)Functions of the muscular system A)Movement: The primary function of skeletal muscle in the body is movement. Even the smallest areas such as the eyeball and the ear have associated mus- cles responsible for their movements. The contraction of skeletal muscle is also important in functions such as breathing and movement of bodily fluids. The stimulation of individual muscle fibers maintains a state of muscle contraction known as tonus. This is important in maintaining the movement of blood and lymph through out the body. When muscle is cut off from nerve supply, a condition that occurs when spinal nerves are severed, the muscles lose tonus and become flaccid and eventually atrophy (shrink). The involuntary contraction of smooth muscle is also essential for movement of fluids and material through the body. Likewise the involuntary pumping of the cardiac muscle keeps blood flowing through the body. B) Body heat production: The body maintains a fairly constant temperature. Physiologically this is one of the principles of homeostasis - the bodys ability to regulate its functions. Muscle metabolism produces heat as an end product. Because muscles constitute about 40-45% of the bodys weight and are in a constant state of fiber activity, they are the primary source of body heat. The rate of heat production rises with increased muscle activity. This also explains why emaciated and elderly people, who have reduced muscle mass have difficulty staying warm....
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This note was uploaded on 05/16/2011 for the course NURSING 112 taught by Professor Brinley during the Spring '11 term at Pace.
- Spring '11