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IB131_9.21.09_Muscles - Generalstructural&functionaltopics...

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600 Human skeletal muscles General structural & functional topics muscle shape & function coordinated actions of muscle groups intrinsic & extrinsic muscles muscle innervation Regional descriptions
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Skeletal muscles – consist of fascicles Skeletal muscles consist of fascicles Fascicles – arranged in different patterns Fascicle arrangement tells about action of a Fascicle arrangement – tells about action of a muscle
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Fusiform thick in middle & tapered at ends biceps brachii Parallel – fascicles run parallel to the long axis of muscle Rectus abdominis Strap like – sternocleidomastoid Circular fascicles are arranged in concentric rings Surround external body openings Sphincter – general name for a circular muscle Examples Orbicularis oris & orbicularis oculi
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Convergent Origin of the muscle is broad Fascicles converge toward the tendon of insertion Example – pectoralis major Example pectoralis major Pennate Fascicles insert obliquely on a tendon Unipennate – fascicles insert into one side of the tendon Bipennate – fascicles insert into the tendon from both sides Multipennate – fascicles insert into one large tendon from all sides palmar interosseus, rectus femoris & deltoid
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Origin attachment to stationary end of muscle Belly h k ddl f thicker, middle region of muscle I i Insertion attachment to mobile end of l muscle
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A muscle cannot reverse the movement it produces Another muscle must undo the action Muscles with opposite actions lie on opposite id f j i sides of a joint
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Prime mover (agonist) Has major responsibility for a certain movement Produces most force Antagonist Opposes or reverses a movement/ prime mover preventing excessive movement and injury Synergist – helps the prime mover Adding extra force d i bl / dif i di i undesirable movements/ modifying direction Stabilizing nearby joint Fixator A f i h h ld b fi l i l A type of synergist that holds a bone firmly in place
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Prime mover (agonist) = brachialis Antagonist = triceps brachii Synergist = biceps brachii Fixator = muscle that holds scapula firmly in place Rh b id Rhomboideus ms.
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Dense fibrous connective tissue divides limb muscles into compartments Muscles in opposing compartments are Agonist and antagonist pairs Each compartment is innervated by a single nerve
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The upper limb has anterior & posterior compartments Anterior arm l compartment muscles Flex the shoulder or arm Innervation is the l musculocutaneous nerve Anterior forearm compartment muscles Flex the wrist and digits Innervation is the median or ulnar nerve
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