Tortora - Chapter 11 - The Muscular System

Tortora - Chapter 11 - The Muscular System - Chapter 11 The...

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11-1 Chapter 11 The Muscular System Skeletal muscle major groupings How movements occur at specific joints Learn the origin, insertion, function and innervation of all major muscles Important to allied health care and physical rehabilitation students
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11-2 Muscle Attachment Sites: Origin and Insertion Skeletal muscles shorten & pull on the bones they are attached to Origin is the bone that does not move when muscle shortens (normally proximal) Insertion is the movable bone (some 2 joint muscles) Fleshy portion of the muscle in between attachment sites = belly
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11-3 Tenosynovitis Inflammation of tendon and associated connective tissues at certain joints wrist, elbows and shoulder commonly affected Pain associated with movement Causes trauma, strain or excessive exercise
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11-4 Lever Systems and Leverage Muscle acts on rigid rod (bone) that moves around a fixed point called a fulcrum Resistance is weight of body part & perhaps an object Effort or load is work done by muscle contraction Mechanical advantage the muscle whose attachment is farther from the joint will produce the most force the muscle attaching closer to the joint has the greater range of motion and the faster the speed it can produce
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11-5 First - Class Lever Can produce mechanical advantage or not depending on location of effort & resistance if effort is further from fulcrum than resistance, then a strong resistance can be moved Head resting on vertebral column weight of face is the resistance joint between skull & atlas is fulcrum posterior neck muscles provide effort
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11-6 Second - Class Lever Similar to a wheelbarrow Always produce mechanical advantage resistance is always closer to fulcrum than the effort Sacrifice of speed for force Raising up on your toes resistance is body weight fulcrum is ball of foot effort is contraction of calf muscles which pull heel up off of floor
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11-7 Third - Class Lever Most common levers in the body Always produce a mechanical disadvantage effort is always closer to fulcrum than resistance Favors speed and range of motion over force Flexor muscles at the elbow resistance is weight in hand fulcrum is elbow joint effort is contraction of biceps brachii muscle
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11-8 Fascicle Arrangements A contracting muscle shortens to about 70% of its length Fascicular arrangement represents a compromise between force of contraction (power) and range of motion muscles with longer fibers have a greater range of motion a short fiber can contract as forcefully as a long one.
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11-9 Coordination Within Muscle Groups Most movement is the result of several muscle working at the same time Most muscles are arranged in opposing pairs at joints prime mover or agonist contracts to cause the desired action antagonist stretches and yields to prime mover synergists contract to stabilize nearby joints fixators stabilize the origin of the prime mover scapula held steady so deltoid can raise arm
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