Circulation & Hemodynamics (DSA) Flashcards
A. Have increased what compared to V.
Elastic fibers, SM, and CT
What is the vol. of blood in the A. Called
Stressed Vol. (under pressure)
Which artery has the highest resistance to blood flow
Arterioles
SM of arterioles is tonically active. What does this mean
Always contracted
What is the SM of the arterioles of vascular beds innervated by and what does this cause
Sympathetic N.S. A1R - causes constriction and increased R
The SM of skeletal muscle arterioles is innervated by what and what does this do
B1 which relaxes and causes increased BF to skeletal muscles with Sympathetic N.S.
How do lipid soluble compounds cross capillaries? What about water soluble (ions)?
Lipid - via simple diffusion
H2O - fenestrations
What is selective perfusion controlled by
Symp. N.S.
What is the volume in the veins called? What do veins have more of compared to A.
Called unstressed vol.
Veins can hold more Vol.
much less elastic fiber than A.
What is the SM of veins innervated by
a1
What is the equation to determine the velocity of blood flow
V = Q/A
What two factors determine blood flow
- Pressure difference between the two ends of the vessel
2. Resistance of the vessel itself
What is considered the “driving force” of blood flow
The pressure difference at the ends of the vessels
Equation to determine pressure difference in a vessel
(Delta)P = QR
The Blood flow of a vessel is directly proportional to what
The change in pressure
Increased pressure means what to flow? What about R
Increased pressure means increased flow
Increased R means decreased flow
Total blood flow is distributed how among parallel vessels
Simultaneously
The total resistance of vessels in series is what? What about BF? Where would you find this in the body?
The sum of all resistances of all vessels
Blood flow is same throughout all types of vessels
Found in specific organs
For vessels in parallel, how to determine total resistance? What about BF? Where would you find this in the body?
Found in A. Branching off Ao.
Total resistance is less than any single resistance
1/Rt = 1/R1 + 1/R2 + 1/R3 etc.
This means that the pressure and flow in each A. Will be aprox. That of the Ao.
For a parallel vessel schematic, what happens if another resistance of the same magnitude is added? What about if a single resistance is increased?
If another one is added, there will be a decreases in total R
However, if one is increased, there will be an increases in total R
What does a reynauds # < 2000 mean? What about >3000?
<2000 - laminar flow (no murmurs)
>3000 - turbulent flow
Why is reynoles # > in anemia? What about with a thrombus?
Anemia - increased bc of decreased blood viscosity
Thrombi - increased bc of occluded vessel
Define vascular compliance and the equation for it
The col. of blood the vessel can hold at a given pressure
C = V/P
Increased compliance means what in terms of volume and pressure
Increased volume and decreased pressure
Veins can withstand what type of pressure and can hold how much volume? What about A.’s?
V.’s can withstand low pressure and can hold high volume
A.’s can withstand high pressure, but hold less volume
A decrease in compliance of the V’s mean a shift where? What about an increase in compliance of the V.’s?
Decreased compliance means a shift to A.’s (stressed volume)
Increased compliance means a shift of blood to V.’s (unstressed volume)
Why does pressure decrease in capillaries
Frictional resistance to BF
Filtration of fluid out of capillary
What is the equation for MAP
MAP = 2/3(DBP) + 1/2(SBP)
OR
MAP = CO x TPR
What does arteriole sclerosis cause in terms of pressure and compliance etc
Increased plaque = decreases r = increased R = decreased compliance = increased systolic, pulse, and mean pressure
Define filtration and absorption
Net movement of fluid out of capillary (+)
Net movement of fluid into capillary (-)
What is the net pressure
The sum of all pressures of the capillary
Define capillary hydrostatic pressure
Favors filtration
Determined by Arteriole and Venule pressure
More affected by venus pressure
Highest at the arteriole end of the capillary
Define interstitial hydrostatic pressure
Favors absorption
Define capillary oncotic pressure
Due to amount of plasma proteins
Favors absorption
Define interstitial oncotic pressure
Favors filtration
What is the equation for EF
EF = (EDV - ESV)/(EDV)
