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11-14-07 anatomy notes

11-14-07 anatomy notes - anatomy notes 1 Muscular System a...

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11-14-07 anatomy notes 1. Muscular System a. Muscle Physiology i. Motor Unit- 1 nerve fiber + ALL muscle fibers it innervates; 2-2000 muscle cells 1. Nerve-hundreds of fibers 2. Groups of nerve fibers from a nerve enter a muscle 3. Each nerve fiber (axon) subdivides into 2-2000 axon branches and these form axon terminals and end feet at the neuromuscular junction 4. Within the neuromuscular junction each end foot associates w/an end plate of muscle fiber 5. An action potential travels along an axon to ALL muscle fibers in a motor unit a. All muscle cells in unit contract at same time ii. Isolated Muscle Preparations 1. Types a. Isomeric-muscle connected at 2 points i. When stimulated, it does NOT move or shorten, ONLY tension increases ii. Because it cannot move, NO work is done in isomeric contraction b. Isotonic-muscle connected at one end and the opposite end is feely movable i. When stimulated it moves, shortens, and does work a. changes shape ii. Work=force X distance a. 5lbs. X 3ft. = 15ft/lb.
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