CHAPTER 10 Notes THE MUSCULAR SYSTEM 2014.doc

CHAPTER 10 Notes THE MUSCULAR SYSTEM 2014.doc - A P 242...

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A & P 242: Human Anatomy and Physiology I Gary Brady / SFCC Life Sciences /2014 Chapter 10 Notes: Muscular System Myology = study of muscles Kinesiology = the study of the movement of muscles Derivation of muscle tissue = MESODERM germ layer Muscle cells are NOT mitotically active. They don't divide. (Note: the smooth muscle of the uterus does divide by mitosis). Muscle biomass = 40 to 50% of total body weight. If 40%: 37% is skeletal muscle and 3% is cardiac muscle. ________________________________________________________ FUNCTIONS OF MUSCLE TISSUE: 1. Produce skeletal movement (motion or locomotion) 2. Maintain posture and body position 3. Support soft tissues 4. Guard entrances and exits to provide voluntary control over swallowing, urination and defecation 5. . Maintain body temperature = thermogenesis (heat production) 6. MOVING SUBSTANCES: a) cardiac muscle MOVES blood b) smooth muscle MOVES food through the GI tract, moves sperm and ova through the reproductive tract and propels urine through the urinary system. c) skeletal muscle MOVES lymphatic fluid and venous blood 7. Communication = Muscles are used for smiling and talking.
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8. Energy storage = skeletal muscle stores carbohydrates as glycogen. (75% of glycogen in the body is located in skeletal muscle; 25% is stored in the liver). _________________________________________________________ CHARACTERISTICS OF MUSCLE TISSUE: 1. Electrical excitability (conductivity) = muscle fibers respond to stimuli by conducting electrical impulses called action potentials. 2. Contractility = muscle contracts and becomes shorter and thicker. This produces movement. 3. Extensibility = ability of the muscle to extend (stretch) without being damaged. 4. Elasticity = muscle tissue is able to return to its original shape after extension or contraction. _________________________________________________________ TYPES OF MUSCLE: 1. Smooth Muscle Action = involuntary App = nonstriated single fusiform-shaped cells, each having one centrally located nucleus. Speed of Contraction = slowest Loc #1 = organs (visceral) Uterus, bladder, small blood vessels, digestive tract (which moves food by peristalsis when smooth muscle contracts). Loc #2 = nonvisceral Arrector pili, large airways, iris of eye, large blood vessels. _________________________________________________________ 2. Cardiac Muscle Action = involuntary App = striated, branched cells containing one or two nuclei per cell. Intercalated discs are in between the cells. They provide strength and aid conduction of nerve impulses. Loc = Heart
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The heart contracts and relaxes rapidly. A long refractory period allows the heart to rest in between beats, preventing tetany. Note: Cardiac muscle has autorythmicity. It contracts without outside stimulation (no outside nerve innervation). _________________________________________________________ 3. Skeletal Muscle Action = voluntary (Can be made to contract and relax by conscious control). App= striated, non-branched and multinucleated. Long, cylinder-shaped fiber with MANY peripherally located nuclei in each cell. Speed of Contraction = fastest Loc = connected to bones by tendons _________________________________________________________ CHARACTERISTICS OF TYPICAL SKELETAL MUSCLE: 1. Origin = the more stationary point of attachment, (the bone that has little or no movement), and is usually the more proximal attachment.
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