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muscle arise from embryonic muscle cells called
myoblasts
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functional unit of striated muscle
sarcomere
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each sarcomere is bounded at either end by a
Z disk
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contains only thick filaments and only myosin
H-zone
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middle of H zone is
m line. contains enzymes that are important in the energ metabolism of muscle fibers
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portiion between 2 A bands and only thin filaments is and actin only
I bands
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muscle contracts when
the cross-bridges on myosin molecules bind transiently to sites on actin molecules, causes myosin to change conformation
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when myosin comlexes are treated with proteolutic enzme trypsin
separate into light meromyosin and heavy meromyosin
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isometric contraction
length of muscle doesnt change
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isotonic contraction
muscle is allowed to shorten
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filamentous protein that runs parallel to actin filaments
tropomyosin
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around the perimeter of each myofibril at the level of the z disk is a hollow membranous tube called
traverse tubule T-Tubule. less 0.1 micrometer in diameter
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four major groups of vertebrate skeletal muscle
tonic fibers and 3 types of twitch fibers(phasic)
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tonic muscle fibers
contract slowly, no twitches, postural muscle no atp
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slow twitch or type I
contract slowly fatigue slowly. contain large number of mitochondrai and have rich blood supply. dark meat
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fast twitch oxidative type IIa
high v max, activate quickly, flight muscles,relativley resistant to fatigue
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fst-twitch glycolytic type IIb
high v-max activate and relax quickly, few mitchondria rely on anaerobic glycolysis for atp, white breast
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causes a joint to close
flexor
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causes joint to open
extensor
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collection of motor neurons that innervate a particular muscle is
motor pool
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represents one alpha motor neuron and all the muscle cells it contacts synaptically
motor unit
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heart contraction is
myogenic, initiated in te muscle fibers themselves
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class of msucles that lack sarcomeres and do not appear striaed when viewed with a micro
smooth muscles
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binds to thin filaments in smooth muscle, prevents binding between myosin and actin.calcium binding regulatory protein role in latch mechanism smooth muscle
caldesmon
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troponin-c structurally like, calcium-binding protein regulatory protein found in all tissues
calmodulin
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red muscles contain
myoglobin and are power muscles, slow
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white muscles
less myoglobin fast but fatigue easy
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striations are created by
myosin and actin overlap
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fascicles
groups of muscle cells, surrounded by perimysium
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