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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