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Lecture 11

ANAT 101 Lecture 11: ANAT CH 11

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ANAT 101
Michael Bruneau

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ANAT CH 11 Muscle Attachment - Skeletal muscles make movement by exerting force on the tendons which then are attached to and pull on bones to make movement - When a muscle contracts, one articulate bone is drawn to the other o One bone is stationary due to other muscles stabilizing the bone by contracting or pulling the other way or because it has a less movable structure while the other bone moves - Reverse muscle action (RMA): actions are reversed in the body; origin and insertion switch Origin and Insertion - Origin: the attachment of a muscles tendon to the stationary bone o proximal - Insertion: the attachment of the muscles other tendon to the movable bone o Distal o Pulled toward the origin - Belly: fleshy portion of muscle between the tendons o Ex: triceps Lever System - Bones are levers and joints are fulcrums - Lever: rigid structure that can move around a fixed point (fulcrum) o Lever is acted on by the effort (causes movement) and the load/ resistance (opposes movement) - Effort: force exerted by contraction - Load: weight of body part being moved or the resistance the body part is trying to overcome - Motion = E > Load - Ex: bicep curl o Elbow Is the fulcrum o Weight of forearm + dumbbell is the load o Force of contraction of the bicep brachii pulling the forearm up is the effort Mechanical Advantage and Disadvantage - Determined by the distance between the fulcrum and load and the point at which the effort is applied - Mechanical advantage: load is closer to fulcrum o Small effort is required to move a large load over a small distance - Mechanical disadvantage: load further from fulcrum and effort applied closer to fulcrum o Large effort needed to move a small load at greater speed Types of Levers 1) First Class a. Fulcrum between the effort and load b. Can make mechanical advantage or disadvantage depending on whether E or L is closer to F c. seesaw 2) Second class a. Load is between the fulcrum and effort b. Mechanical advantage b.i. Load closer to fulcrum b.ii. Favors force c. Makes most force d. Ex: calf raise 3) Third class a. Effort between fulcrum and load b. Mechanical disadvantage b.i. Favors speed and range of motion c. Ex: bicep curls Fascicle Arrangement - Muscle fibers are parallel and arranged in bundles called fascicles - Fascicles are in different patterns w/ respect to the tendon: o Parallel  Greater range of motion and less power  Parallel to longitudinal axis of muscle  Terminate at either end in flat tendons  Ex: sternohyloid muscle of the neck o Fusiform (narrow ends and wide middle)  Nearly parallel  Terminate in flat tendons  Ex: digastric muscle o Circular  Concentric circular arrangement  Form sphincter muscles o Triangular  Spread over broad area at thick central tendon  Ex: pec major o Pennate (feather)  Short fascicles  More power and smaller range  Unipennate:  Fascicles arranged on one side of the tendon  Bipennate:  Fascicles arranged on both sides of centrally positioned tendons  Multipennate:  Fascicles attach obliquely from many directions to several tendons - Fascicle arrangement affects the muscles power and range of motion o Longer fiber = greater range of motion o More fibers per unit of cross sectio
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