Baroreceptors and reflexes Flashcards
Why is it useful for flow autoregulated in most vascular beds?
to match metabolic demand
to be independent of perfusion pressure
what determines local blood flow?
tissues not the heart
how is local blood flow controlled and why is this possible?
local blood flow controlled by local resistance, as reflexes hold arterial blood pressure constant
controlling heart rate or stroke volume will not regulate flow
what is the equation for tissue blood flow?
how do you calculate resistance?
tissue blood flow = (arterial BP - venous BP)/resistance
resistance = length of vessel / (radius of vessel)^4
What factors can affect blood pressure?
cardiac contraction: hormones, nerves, Starling’s law
water/salt balance: blood volume (urine, sweat, drink)
vessel compliance (veins): pressure-volume relationship
what happens to resistance when cardiac output increases?
resistance increases to accommodate
what ensures the constancy of pressure?
baroreflexes
what ensures the constancy of pressure?
baroreflexes
what is Poiseuille’s law?
resistance ~ 1/radius^4
If you divide the vessel radius by 2, what happens to resistance?
resistance increased by 16x
How do you decreased blood pressure downstream using vascular smooth muscles?
VSMs have basal tone and if you remove calcium from the muscle cells via pumps they will relax. relaxing the smooth muscle decreases downstream pressure
How does vasoconstriction affect BP and capillary perfusion
Causes arterial BP before the constriction site to increase and capillary perfusion to decrease.
what does vasoconstriction and dilation allow us to do?
alter blood flow through different tissues dramatically
