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16 Cards in this Set

  • Front
  • Back
Smooth Muscle Structure
-consists of small cells linked by desmosomes

-no straiation

-filament-parallel-not in registration
Smooth Muscle Structure
- thin-tropomyosin and actin

-no troponin

-TM doesnt block A.M. contact

-ATPase myosin
smooth muscle strucure
-dense bodies
-in interior and on membrane

-thin filaments attached to dense bodies (equiv to 2-lines)
-smooth muscle contraction with NO stimulus

-Ca2+ leak produces 10-15% maximum force
Smooth muscle contraction
-different than skeletal muscle
smooth muscle contraction
-Calcium sources
-most:through Ca2+ channels from outside

-some:released from small SR by IP3
smooth muscle contraction
-Myosin Light Chain Kinase (MLCK)
-myosin light chain are small proteins attached to the head

-MLCK add phosphate to myosin light chains

-MLC-P -> activate myosin ATPase -> actin to produce force
smooth muscle contraction
-force generation
A + M x ADP x Pi -> A x M x ADP x Pi

A x M -- force

ADP + Pi --slow ATPase activity
smooth muscle contraction
-Myosin Light Chain Phosphate (MLC-Pase)
-take phosphate off MLC

-high Ca2+ contracted
A x M-P ---> A x M
contract latch

-myosin stays attached 20x longer then when phosphorylated
Smooth Muscle Types
-2 major functions:
empty cavity Or
maintain force indefinitely
Smooth muscle types
-visceral (single unit) SM
-connected by gap junctions: electrically connect cells

-electrical activation: neural, intrinsic, open Na+ channels, close K+ channels spontaneously

-1 AP spreads throughout the tissue -> cavity empties
smooth muscle types
-visceral(single unit) SM
-Neural Effects
-parasympathetic neurons release Ach - cause contraction

-sympatethic neurons realease NE - cause relaxation
smooth muscle types
-Multi-Unit SM
-no gap junctions - every cell independent of every other cell

-blood vessels, eye -> maintain contraction

-greater variation in force
smooth muscle types
-multi-unit SM
-very important

-partial activation allows either more or less force

-latch reduces energy output
smooth muscle types
-multi-unit SM
-Neural Effects
-most:only sympathetic neurons innervate multi-unit smooth muscle

-alpha receptors will contract to NE (inc Ca2+)

-Beta 2 receptors will relax to NE (dec Ca2+)