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36 Cards in this Set

  • Front
  • Back
3 types of muscle
Skeletal
Cardiac
Smooth
Basic unit of skeletal muscle
Fiber
Basic unit of cardiac and smooth muscle
Cell
General characteristics of skeletal muscle
MULTINUCLEATED SYNCITIUM
Formed by fusion of small myoblasts
Diameter 100-100 microns
Length can be from few millimeters to meter
Cell membrane- sarcolemma (nuclei are under)
Cross striation
3 types of connective tissue in skeletal muscle
Endomysium
Perimysium
Epimysium
Endomysium
Thin layer of reticular fibers surrounding individual muscle fibers
Contains capillaries and smallest nerve fibers
-almost undetectable
Perimysium
Thicker connective tissue layer surrounding bundles of fibers (fascicle)
Contains large blood vessels and nerves
Epimysium
Sheath of dense connective tissue surrounding collection of fascicles
Carries major vascular and nerve supply
2 types of muscle fibers in skeletal muscle
Red and white
Red fibers
-Small
-A lot of myoglobin and mitochondria
-Great resistance to fatigue
-Less muscle tension
-Slow twitch motor units
-Found in leg and breast of migrating birds
White fibers
-Large
-Little myoglobin and mitochondria
-Fatigue rapidly
-Large peak muscle tension
-Fast twitch motor unit
-Precise control
-Extraocular muscles, finger muscles
Intermediate fibers
Intermediate size and myoglobin levels
Muscle fascicle
Bundle of fibers
Myofibril
Structural and functional unit of muscle
Syncitium
Thick myofilament
-Myosin II composed of two heavy polypeptide chains and four light chains
-Globular myosin head has binding sites for ATP and actin
F actin
double helix, composed of G actin subunits
Tropomyosin
two double helix polypeptide chains - masks myosin binding site of actin in resting muscle
Troponin C binds..
Ca
Troponin T binds..
to tropomyosin
Troponin I binds..
to actin, inhibiting actin myosin interaction
A band is mostly
dark band, mostly thick myosin filaments in relaxed muscle
I band
isotropic, light band (mostly thin filaments of actin)
Z line
darker line at the middle of I line
Sarcomere
Portion of myofibril between two Z lines, basic contractile unit of striated muscle
M line
Middle of sarcomere
In contraction I line
decreases
Alpha actinin, desmin and nebulin
anchor thin filaments in Z line
Titin
anchors thick filaments in Z line
Tropomodulin
maintains length of actn filament
Myomesin and C protein
hold thick filaments aligned at M line
Dystrophin
anchors actin to laminin
Absense of dystrophin results in
Duschenne dystrophy
Terminal cisterna stores
Ca
T tubules
Penetrate into muscle fibers and regulate Ca channels
Triad
T tubules and adjacent terminal cisternae at border of A and I bands
What triggers Ca release from terminal cisternae
Depolarization of T tubule