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a band
The component of the sarcomere that appears darker because it contains thick filaments and areas in which the thick and thin filaments overlap.
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Actin
A bead-shaped contractile protein found in muscle fibers and motile cells
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Elastic Filamet
A myofilament that consists of the structural protein titin.
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Endomysium
meaning within the muscle, is a wispy layer of areolar connective tissue that ensheaths each individual myocyte
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Epimysium
a sheath of fibrous elastic tissue surrounding a muscle.
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i band
The component of the sarcomere that appears lighter because it contains only thin filaments.
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h zone
the zone of the thick filaments that is not superimposed by the thin filaments.
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m line
the attachment site for the thick filaments
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Motor End Plate
The specialized region of the skeletal muscle fiber plasma membrane that contains receptors for acetylcholine.
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Muscle Fiber
An alternate name for a skeletal muscle cell.
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Myofibril
Long, cylindrical organelles composed of muscle proteins in a muscle fiber.
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myosin
A club-shaped contractile protein found in muscle fibers and motile cells
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neuromuscular junction
The location where a neuron communicates with a muscle fiber.
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Sarcolemma
The plasma membrane of a muscle fiber.
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Sarcomere
The functional unit of muscle contraction; consists of the area of the myofibril from one Z-disc to the next Z-disc.
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Sarcoplasmic Reticulum
The specialized smooth endoplasmic reticulum of a muscle fiber that stores calcium ions.
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terminal Cisternae
Enlarged regions of the sarcoplasmic reticulum where it contacts T-tubules.
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thick filament
A myofilament composed of many molecules of the protein myosin.
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thin filament
A myofilament composed of molecules of the proteins actin, troponin, and tropomyosin.
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triad
the structure formed by a T tubule with a sarcoplasmic reticulum (SR) known as the terminal cisterna on either side.
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tropomyosin
a protein involved in muscle contraction. It is related to myosin and occurs together with troponin in the thin filaments of muscle tissue.
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troponin
a complex of muscle proteins which, when combined with Ca++, influence tropomyosin to initiate contraction.
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