Blood flow and metabolism Flashcards
(44 cards)
Pressure that is the difference between inside snd outside of the capillaries
Transmural pressure
When lung volume increases, blood vessels increases their diameter hence pressure is _______
decreased
formula of vascular resistance
(input pressure-output pressure)/blood flow
about 1.7 mmhg/l/‘in
(15-5)/6
increase in pulmonary arterial or venous pressure causes pulmonary vascular residtanse to
FALL
term used as the pressure rises and vessels begin to conduct blood lowering resistance
chief mechanism for the fall in pulmo vascular resistance
Recruitment
2 mechanisms for decrease in pulmonary vascular resistance as vascular pressures are raised
Recruitment (opening of prev closed vessel)
Distension (inc in caliber)
predominant mechanism for the fall in PVR at high vascular pressure
distention
When lung volume is low, extra alveolar vessel has __________ resistance
HIGH resistance
at high lung vol, capillaries are stretched and caliber is reduced hence ______ in resistance
increase
Substance causing contraction of the Smooth muscles increasing PVR
serotonin
histamine
norepinephrine
endothelin
relaxes smooth muscles in pulmonary circulation
PD inhibitors
calcium channel blockers
Prostacyclin PGI2
acetylcholine
in exercise, PVR
decreases
(recruitment and distention of capillaries)
PVR increases at ______ lung volume
low
Measurement if pulmo blood flow can be measured using what principle
Fick principle
waterfall effect is also called
Starling resistor
sluice
flow in zone 3 is determined by
arterial venous pressure difference
increased in blood flow in zoe 3 is due to _______. of capillaries
distention
in zone 3, transmural pressure _______ and mean width ______
both increases
Which zone of the lung , where parenchyma is least expanded hence reduced blood flow
zone 4
(narrowing of extra alveolar vessels when lung is poorly inflated)
what causes unevenness of blood flow in the lung
randome arrangement of blood vessels and capillaries
blood flow along acinus, periphery
decreases
level or value of alveolar po2 where there will be a marked vasoconstriction
70mmhg
Major trigger for smooth muscle contraction
increase in cytoplasmic calcium ion concentration
how does nitric oxide helps in vasodilation of smooth muscles?
activates guanylate cyclase
increases CGMP
inhibiting rise in intracellular calcium
