Biology > STUDY GUIDE > Biology (BIOL 235) Chapter 11-18 typed notes (All)

Biology (BIOL 235) Chapter 11-18 typed notes

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Chapter 11.1 How skeletal muscles produce movements. 1. Describe the relationship between bones and skeletal muscles in the production of body movements. Skeletal muscles that produce movements... do so by exerting force on tendons which in turn pull on bones or other structures (such as the skin). Most muscles cross at least 1 joint and are usually attached to articulating bones that form the joint. When a skeletal muscle contracts, it moves one of the articulating bones. Usually the bones do not move equally in response to the contraction. 1 bone remains stationary near its original position because other muscles stabilize it or because its structure makes it less movable. A. Origin – the attachment of a muscle’s tendon to a stationary bone or the end opposite the insertion. B. Insertion – the attachment of the muscle’s other tendon to the movable bone or the end opposite the origin. Analogy: spring on a door frame: the end attached to the frame is the origin, the end attached to the door is the insertion. Rule of thumb: the origin is usually proximal, and the insertion is usually distal. The insertion is usually pulled toward the origin. C. belly (body) – the fleshy portion of the muscle between the tendons. D. Actions – the main movements that occur when the muscle contractions. In spring door example: closing of the door. E. reverse muscle action – during specific movements of the body, the actions are reversed. Therefore the positions of the origin and insertion of a specific muscle are switched. Lever systems and leverage (fulcrum, effort, load/resistance) A. lever – rigid structure that can move around a fixed point called a fulcrum B. fulcrum – fixed point around which a lever can move. C. Effort – force which causes movement, exerted by muscular contraction. [Show More]

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