Striated Muscle

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Striated Muscle

Post by Dr Sarhan on Thu Jan 17, 2008 9:21 am

Structure


Whole Muscle or Heart - Composed of many individual muscle fibers (cells)
Single muscle Fiber (Cell) - Striated appearance under light microscope.
Myofibril - Striated in appearance and is made up of a series of sarcomeres.


Sarcomeres


Composed of myofilaments (contractile protein filaments) whose highly organized arrangement results in the striations observed in the single muscle fiber.
Striation Pattern
a) A Band - composed of thick and overlapping thin filaments.
b) I Band - composed of thin filaments.
c) Z Line - connects adjacent sarcomeres and anchors thin filaments.


Myofilaments


Composed of myofilaments (contractile protein filaments) whose highly organized arrangement results in the striations observed in the single muscle fiber.

a) Thick filaments - The thick filament is composed of myosin. The projections from the myosin filament are called crossbridges. The crossbridge is believed to be a molecular motor that converts chemical energy into mechanical work.
b) Thin filaments - The thin filament is composed of actin, troponin, and tropomyosin. The cyclic attachment and detachment of myosin crossbridges to actin produces muscle active force and/or shortening. The troponin and tropomyosin comprise the calcium sensitive regulatory proteins. In the absence of intracellular calcium, the troponin/tropomyosin prevent the interaction of actin and myosin.
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Dr Sarhan
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