Tuesday, May 29, 2012


1.     Briefly highlight the contraction of the smooth muscles
Calcium ions come from outside the cell. They bind to calmodulin in the cytosol and then bind to an enzyme on myosin called Myosin Light Chain Kinase which uses ATP to transfer a phosphate to myosin. The phosphate activates the myosin which then forms cross bridges with actin. When ca++ is pumped out of the cell, the phosphate gets removed from myosin by another enzyme. Myosin becomes inactive and the muscle relaxes.
2.     State the characteristics of smooth muscle
-more actin than myosin
-no striations
-spindle shaped
-no sarcomeres
-fatigue resistant
-activation is involuntary
-innervation is by ANS
-located in blood vessels, gastro-interstinal tract, urinary bladder, respiratory tract, iris of the eye and reproductive organs
-External longitudinal layer-runs parallel to the organs long axis and shorten and widen the lumen when it contracts
-Internal circular layer-runs around the circumference of the organs axis lengthens the tube but narrows the lumen when contracted
3.     State the characteristics of skeletal muscles
-Excitability- capacity of the muscle to respond to stimuli
-Extencibility-abilty of the muscle to stretch back to its original length
-Contractility- ability of the muscle to shorten and generate a pulling force
 -Elasticity- ability of the muscle to recoil to its original resting length after stretch.

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