AN SC 310 - 16
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What is the flow rule?
Flow = change in P divided by R
What is bulk flow?
Flow due to pressure gradient
How is the pressure gradient calculated?
Pressure in aorta - pressurein vena cava just before it empties into R atrium
What is the mean arteriole pressure (MAP)?
90 mm Hg
What is the central venous pressure (CVP)?
0 mm Hg
What is the pressure gradient of the systemic circuit?
MAP - CVP = 90 - 0 = 90 mm Hg
What is the pressure gradient of the pulmonary circuit?
- Pulmonary arteriole pressure = 15 mm Hg
- Pulmonary venous pressure = 0 mm Hg
- PAP - PVP = 15 - 0 = 15 mm Hg
What factors affect resistance?
What is Poiseuille's Law?
- Flow = (pi)(deltaP)(r4) / 8nL
- n = viscosity
How do pressure gradients and resistance in systemic circulation relate? (eqn)
Flow = deltaP/R
- Flow = cardiac output
- deltP = mean arterial pressure
- R = total peripheral resistance
CO = MAP/TPR
Why are arteries a pressure reservoir?
- Thick elastic arterial walls
- Low compliance
- Expand as blood enters during systole
- Recoil during diastole
What is compliance?
Measure of how the pressure of a vessel will change w/ a change in volume
Low compliance means small increase in vol causes large increase in pressure
High compliance means lg increase in vol reqd to produce lg increase in pressure
What is arterial blood pressure?
Pressure in aorta
What vessels regulate resistance?
What is the pressure drop in arterioles (artery end to cap end)?
90 to 40 mm Hg
What is organ blood flow?
Organ blood flow = MAP/organ resistance
How does norepinephrine affect arteriole smooth muscle cells?
- Binds to alpha adrenergic receptors
How does epinephrine affect arterioles?
- Binds to alpha and beta2 receptors
- alpha - vasoconstriction
- beta2 - vasodilation
How does epinephrine concentratoin affect arteriole radius?
Lower  - binds to beta2 = vasodilation
- Higher  - binds to alpha and beta2 = vasoconstriction & dilation
- Vasoconstriction dominant
What are the 3 hormones that control arteriole radius & map? Where do they originate?
- Epinephrine - adrenal medulla
- Vasopressin = ADH - posterior pituitary
- Angiotensin II - synthed from angiotensinogen
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