Muscle Terms Flashcards
Definition of
Striated muscle (def)
“striped” (alternating light & dark bands in micrographs) - skeletal & cardiac muscle
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Triad (def)
T-tubule and flanking terminal cisternae (in skeletal muscle)
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Muscle (def)
Bundle of fascicles
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Smooth muscle (def)
Non-striated muscle
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Z disk (sarcomere) (def)
Band at end of sarcomere to which terminal actin molecules on adjacent sarcomeres are bound
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Motor Endplate (def)
Highly excitable region of the sarcolemma, at the neuromuscular junction
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Muscle fiber (def)
Bundle of myofibrils (one cell, surrounded by sarcolemma, containing sarcoplasm)
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Terminal cisterna(e) (def)
Chamber(s) of SR alongside (adjacent to) T-tubule
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Perimysium (def)
Collagenous connective tissue surrounding one fascicle
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Myosin filament (def)
Many 100’s of myosin molecules
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Basal lamina (def)
Matrix with glycoproteins and collagen, between the endomysium and muscle fiber plasma membrane
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Sarcomere (def)
Contractile unit of myofibril; contains alternating actin & myosin filaments; ends “capped” by Z-disks
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M line (sarcomere) (def)
Center line of sarcomere
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Epimysium (def)
Dense collagenous connective tissue; surrounds one muscle
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Sarcolemma (def)
Myofiber plasma membrane
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T-tubule (def)
Sarcolemma invagination, perpendicular to myofibrils
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Muscle Fascicle (def)
Bundle of myofibers; surrounded by perimysium
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Myofilament (def)
Actin, myosin (and intermediate filaments)
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Endomysium (def)
Fine (fuzzy-looking) connective tissue surrounding one muscle fiber
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A-band (sarcomere) (def)
Along entire length of myosin filaments (in middle of cell)
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Ryanodin receptor (def)
Ca++ gated Ca++ release channel, located on SR (on cisternae adjacent to T-tubule in striated muscle (in contact); beneath caveolae in smooth muscle (not in contact but very close))
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I band (sarcomere) (def)
Region where there are actin filaments only - no over-lapping myosin filaments (ends of each sarcomere)
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Myosin molecule (def)
4 light chains and 2 heavy chains; 2 heads with 2 active sites each (one for ATP, one for actin)
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Arrows (w.r.t. myotendinous junction) (def)
Projections of myofibers inserted into connective tissue
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Sarcoplasm (def)
Myofiber cytoplasm
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Dihydropyridine receptor (def)
Voltage-gated Ca++ channel, on T-tubules
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Myofibril (def)
Sarcomeres lined end-to-end
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H zone (sarcomere) (def)
Region where there are myosin filaments only - no overlapping actin filaments (middle of each sarcomere)
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Myocardium (def)
Thick layer of cardiac muscle in heart
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Caveola(e) (def)
Smooth muscle: goblet-shaped plasma membrane invagination (instead of T-tubules)
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Dense body (def)
Anchor point for filaments in smooth muscle, located in sarcoplasm
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Zonula adherens (def)
Component of transverse region of intercalated disks; bind f-actin of terminal sarcomeres to plasma membrane
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Calmodulin (def)
Smooth muscle protein; binds Ca++ released from SR, then binds MLCK
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Dense plaque (def)
Anchor point for filaments in smooth muscle, located on sarcolemma
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Intercalated disk (def)
Junctional complex between cardiomyocytes
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Desmosomes (def)
Component of transverse region of intercalated disks; keeps adjacent fibers together during contraction
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MLCK (def)
Myosin light chain kinase; when activated (by binding Ca++/calmodulin), phosphorylates 2 myosin light chains to permit myosin contraction
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Varicosity (def)
Swelling in autonomic smooth muscle motor neuron; contains mitochondria and vesicles of neurotransmitter
