Sunday, December 14, 2008

Contraction in Smooth vs. Skeletal Muscle

Smooth muscle



Smooth muscle is a type of non-striated muscle, found within the tunica media layer of large and small arteries and veins, the bladder, uterus, male and female reproductive tracts, gastrointestinal tract, respiratory tract, the ciliary muscle, and iris of the eye. The glomeruli of the kidneys contain a smooth muscle-like cell called the mesangial cell. Smooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure, function, excitation-contraction coupling, and mechanism of contraction.

* Cystolic Ca2+ binds with calmodulin in cytosol
* Ca2+ calmodulin complex binds to myosin light chani kinase
* myosin light chain kinase used ATP to phosphorylate myosin cross bridges.
* Phosphorylated cross bridges bind to action filaments
* Cros-bridge cycle produces tension and shortening







Skeletal muscle



Skeletal muscle is a type of striated muscle, which usually attaches to tendons. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction. They generally contract voluntarily (via somatic nerve stimulation), although they can contract involuntarily through reflexes. The whole muscle is wrapped in a special type of connective tissue, epimysium.

* Cytosolic ca3+
* ca 2+binds to troponin on the filaments
* Conformatioal change in troponinm moves tropomyosin out of blocking position
* Mysosin cross bridges bund to action
* Cross-bridge cycle produces tension and shortening



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