Circulation and Hemodynamics DSA Flashcards
What receptors are found most commonly found in arterioles? What is their effect
alpha1- adrenergic –> elicit contraction of sm m
What receptors are less commonly found in arterioles? What is their effect?
Beta2-adrenergic found in arterioles of skeletal m –> elicit relaxation of sm m and vasodilation
What type of vessel has the largest area to blood volume ratio?
capillaries
What is perfusion of capillaries determined by?
metabolic needs of tissues controlled by sympathetic NS
What type of blood is in veins and venules? What percentage of total blood is there?
unstressed volume of blood 65% at any given time
What type of receptors are in venules and veins?
alpha1-adrenergic –> constrict veins and redistribute blood to stresss volume
Where is velocity in circulation the greatest?
“at the ends” = largest arteries and veins, closest to the heart
What is blood flow determined by?
volume and velocity “more cars in the tunnel, the speed will decrease”
What is the equation for blood flow?
Q = deltaP/R
What is series resistance?
total resistance is the sum of individual resistances
What is paralell resistance?
total resistance is less than any of the individual resistances
What is laminar flow?
velocity is greatest at the center and least toward vessel walls more efficient than turbulent flow
What is turbulent flow?
when laminar flow is disrupted and takes more energy to drive audible as bruits in arteries or vascular channels and can indicate stenosis
What is the eqn for Reynold’s number?
Nr = (rho * d * v) / eta rho = density of blood d = diameter of vessel v = velocity eta = viscosity of blood
What is reynold’s number used for?
to predict whether flow will be turbulent or laminar < 2000 = laminar
What is shear?
occurs bc velocity is not the same along the vessel wall as it is in the center shear is greatest along wall and lowest at center
What is compliance of blood vessels? How is it graphed?
distensibility of a vessel graphed on a volume vs pressure graph
What vessels have the greatest and least compliance?
greatest = veins least = arteries
What happens if the compliance of a vein is decreased?
vasoconstriction = decreased compliance –> redistribution of blood from unstressed volume to stressed volume (arteries)
Where is mean pressure greatest? Where is it the smallest?
largest in aorta smallest in arterioles
What is pulse pressure?
difference btw systolic and diastolic pressures
What is mean arterial pressure?
2/3(DBP) + 1/3(SBP) = 1/3(pulse pressure) ends up falling closer to diastolic
How does arteriosclerosis affect blood pressures?
increases systolic, pulse pressure, and MAP doesn’t affect diastolic
How does aortic stenosis affect blood pressures?
systolic, pulse pressure, and MAP will all be decreased
How does venous pressure change throughout the body?
lower than arterial and nears zero at vena cava and right atrium
How does pulmonary circulation compare to systemic?
much lower pressures flow is the same so resistance is much lower right heart doesn’t have to achieve as large of a pressure
How does arterial pressure vary btw recumbent and upright?
fairly consistent recumbent standing = much lower at head and higher at feet
What would happen if you had an instantaneous increase in cardiac output or peripheral resistance?
arterial blood volume will continually increase until arterial pressure reaches a level of 200 mm Hg
What are the 5 types of microcirculation?
simple diffusion lipid soluble (gases) water soluble osmosis proteins (generally don’t cross except for kidney and intestines)
What is the Starling Equation?
Jv = Kf[(Pc-Pi) - (πc - πi)]
Jv = fluid movement
Kf = magnitude of fluid mvnt
Pc = capillary hydrostatic pressure
Pi = interstitial hydrostatic pressure
πc = capillary oncotic pressure
πi = interstitial oncotic pressure
What does positive value mean in Starling eqn?
Which variables are typically positive?
favors filtration = fluid from capillary –> tissue
capillary hydrostatic pressure (Pc)
Interstitial oncotic pressure (πi)
What does a negative value mean in starling eqn?
What variables are typically negative?
favors absorption = fluid back into capillary
Interstitial hydrostatic pressure (Pi)
Capillary oncotic pressure (πc)
What can cause an increased Pc?
venous constriction, increased venous P, edema
What can cause a decreased πc?
decreased plasma protein, severe liver failure, nephrotic syndrome
What can cause increased Kf?
burns, inflammation
