The Vascular System Flashcards
Where does most of the blood sit at rest?
Venous system
inf. Vena cava
How much blood sits in the venous system?
61%
A = 12
B = 9%
C = 11%
D = 7%
E = 61%
What does the heterogeneity of the vascular network allow?
Adapt to environment
blood vessels different in nerves (parallel), muscles (cork screw), lung for example
What controls the blood pressure
Contractility of the vascular smooth muscle cells
What are vascular smooth muscle cells embedded in?
Collagen and elastin
Name the 2 cell types of smooth muscle
What allows the contraction of a smooth muscle cell?
Actin and myosin
What is the thick filament?
Myosin
What happens if the smooth muscle cells are not flexible (no collagen and elastin matrix)
Damage to blood vessels
What regulates cross bridging in smooth muscle?
MLCK
Myosin light chain kinase
Myosin light chain
What does the light chain inhibit?
The myosin binding to the actin via the heavy chain
How do we activate myosin?
Calmodulin binds calcium = complex
This binds MLCK
Phosphorylated the myosin light chains
Confo change in the light chain and expose actin BS
Actin BS on myosin exposed
Contraction activated
What muscle has myosin light chain?
Smooth muscle
What receptor regulates smooth muscle contactility?
Voltage gated Ca2+ channels
What does calcium into the cell activate?
Myosin light chain kinase
What are 2 ways calcium can increase in the cell?
Extracellular via the voltage gated calcium channels
Intracellular calcium stores
What activates the intracellular calcium stores?
PLC pathway
then IP3 activates the Ca2+ channels
What does a drops in CO2 do to smooth muscle?
Dilation - allow ,ore blood to get into cerebral circulation
Why do you pass out during hyperventilation?
Blood vessels contract
What happens to blood vessels in decreased CO2?
Vasoconstriction
What happens to cerebral blood flow during hyperventilation?
Cerebral blood flow halves
In pulmonary circulation, during hypoxia what happens to blood vessels?
Vasoconstriction
As that part of the lung isn’t working properly
In systemic circulation what is the effect of hypoxia on blood vessels?
Vasodilation
Increase blood flow
What are 4 factors which regulate vascular smooth muscle contractiliy?
Autonomic nervous system
Endothelial derived factors
Myogenic response
Blood borne factors
In the regulation of smooth muscle contractility, what is the ANS mostly?
Sympathetic
What does NO released from?
Endothelial cells
What is the effect of norepinephrine?
Contract
What is the effect of epinephrine?
Relax
What receptors does norepinephrine act upon?
Alpha adrenergjc
What receptor does epinephrine act upon?
Beta-adrenergic
What is the effect of NO?
Relax
What is the effect of endothelin released from the endothelial cells?
Contract
What are the endothelial-derived factors?
NO
endothelin
What is the half life of NO?
2-5 seconds
What is the limiting factor in NO production?
NOS
NO synathse
What are the 3 forms of NOS?
eNOS
iNOS - inducible form
nNOS
What are the activators of NOS?
Shear stress
Thrombin
ACh
What does shear stress induce?
Activates a kinase enzyme (Akt) which stimulates eNOS
what is the capacitance vessel?
vena cava
what vessels regulate the blood pressure?
arterioles
Do arteries or veins have a large gap between the endothelial cells?
arteries for exchange
what produces the ECM in smooth muscle cells?
the smooth muscle cells, maintain their own flexibility
how do you reverse the depolarisation of the smooth muscle cells?
calcium-activated potassium channels
What agonists activate the intracellular calcium store pathway?
norepinepherine
What is the myogenic response?
innate ability of vascular smooth muscle to respond to changes in pressure
What activates shear stress?
blood flow over endothelial cells
What does NO activate in smooth muscle cells to cause relaxation?
GC which makes cGMP = relaxation
What enzyme makes edothelin-1?
endothelin-converting enzyme
What stimulus causes the production and release of endothelin?
thrombin
GF
angiotensin II
low shear forces
What happens when you double the pressure in the arteries?
active contraction - lumen diameter decreases
myogenic response
What is the stimulus for myogenic response?
vessel wall tension
What is the role of the myognic response?
maintain a constant tissue blood flow when blood pressure changes
When does the myogenic response when blood pressure increases?
cause vascular smooth muscle increase contraction
