Peripheral Circulation And Regultion Of Flow Flashcards
Distinguishing characteristics of smooth muscle
Can maintain tension for prolonged periods at a low energy cost
Contract and relax more slowly
Develop active tension over longer range of lengths (L - T relationship)
Can be activated by stretch (myotonic response)
Can change contractile activity in absence of changes in membrane potential
Characteristics of smooth muscles resting membrane potential
RMP is between -50 to -70 mV
Several K+ channels have been identified
- inward rectifier, ATP dependent K+ channel
Some cells spontaneously generate action potentials or spontaneous membrane oscillations
Action potentials are initiated primarily by Ca++ influx via slow type Ca++ channels
vascular smooth muscle contraction
Calcium - cal modeling activates myosin light chain kinase (MLCK)
MLCK phosphorylase so myosin light chain (MLC) in the presence of ATP
MLC are 20-KD regulatory subunits myosin heads
MLC phosphorylation leads to cross-bridge formation
No troponin
Vascular smooth muscle relaxation
Decreases in intracellular Ca++ cause MLCK dephosphorylation
local vasodilators increase intracellular cGMP inhibiting Ca++ influx/increase K+ currents
B2 receptor binding and increases in cAMP triggers Ca++ transfer to extra cellular space/inhbits MLCK phosphorylation
Norepinephrine from sympathetics bind to
Alpha - adrenergic receptors
Intrinsic mechanisms are ___________________ of CNS or hormonal regulation
Independent
Intrinsic mechanisms
Metabolic regulation
Myotonic mechanism
Mechanical compression
Endothelial dependent regulation
Most potent vasoconstrictor
Endothelin
What produces endothelin
Endothelial cells
Receptors of endothelin
ETa and ETb
ETa receptors mediate
Vasoconstriction inotropic and chronotropic effects
ETb receptors mediate
Vasodilation
Coronary flow during systole is
Primarily compromised on the left side
Nitric oxide
Vasodilator released by endothelial cells acts on adjacent smooth muscle layer (increases cGMP)
