Cv 2 Vessels Flashcards
When BP changes in respect to arterioles changing size
If 1 changes BP wont change. If all change- constrict, BP up, all relax, bp down
How much relative blood volume in veins
2/3
Why high CO is issue in anemia
Already low 02, high CO will lead to less time spent for oxygen exchange
Biggest players in vascular resistance and why
Arterioles- control flow
Capillaries- small size
Which organs get most flow (Q)
Heart 4%, but uses larger proportion of it than brain (gets 13%)
Liver and GI 24%, liver filters
Muscle 21%, increases if running
Kidney 20%, filters
Skin 18%
Which organs use 02 the most VO2
Brain, 21%. Uses less than heart per proportion (heart 11%)
Kidney is active, liver and gi average, skeletal muscle average
When running where does CO leave and go to
Leaves liver and GI, goes to muscles
How to calculate map:
P___ + (__-___ / ___)
Pdiastolic +
Systolic- diastolic
___________________
3
Can never have higher pressure on average higher than where
Inside of heart, farther away from hydrostatic pressure and lose it to gravity
Big drop in average pressure where
Small pressure drop
Almost no pressure drop
Arterioles
Capillaries
Veins
What is poiseueille’s law
R (resistance)=
N (viscosity) x L (tube length) x 8
____________________________
Pi x r (radius) ^4
Relationship to resistance
Radius
Tube length
pressure difference
Radius inc- less resistance, dec more resistance
Longer tube will have more resistance
More pressure difference less resistance.
What happens as radius doubles
Flow increases to a factor of 16 (r to 4th)
What happens as tube length doubles to flow
Flow cut in half, flow= 1/length
Flow= __ x ___ x __
Height of column
Density
Acceleration of gravity
What happens when height of one tube twice as high as other
Pressure twice as great, twice as much flow
What happens when tubes have same height of fluid (effect on flow)
Pressure difference is 0 so flow is 0
Flow in tube with length 1 vs tube with length 2
Flow twice as great in flow with length 1
What happens to flow as viscosity doubles
Flow cut in half
What happens when we double radius to flow
Increase flow by factor of 16
Where radius changes play into effect in physiology
When radius isn’t a limiting factor
Small changes in arterioles have big changes in flow and resistance downstream.
When volume isn’t full (flow of blood through vessel is limiting factor)
What happens to viscosity as hct increases
Viscosity increases
How SVR impacted by hematocrit
Less hematocrit= easier to push= less SVR
Opposite for more SVR
Overall effect of viscosity
What impacts viscosity in different areas of the body
What is lowest possible viscosity of blood
Size of the vessel
Small tube- rbcs line up better, less viscosity than in larger tube
Same as plasma but has to be higher than that
Resistance through network is what in series
Same as the sum of the individual resistors
Resistance through network is what when in parallel
Sum of the reciprocal of the individual resistances
Relationship between velocity and area in vessels
Velocity is inverse of area
Which cross sectional area bigger: aorta or sum of its branches
Sum of its branches
What happens to velocity as aorta goes into branches
What happens to velocity as capillaries form into veins
Velocity decreases, surface area increases
Velocity increases, surface area decreases
Purpose of velocity decrease in capillaries
Spends more time there, better for diffusion
Which is bigger in area:
Veins or arteries
Arterioles or capillaries
Aorta of vena cava
Veins
Capillaries
Vena cava
Effect of turbulent flow on pressure difference
Increase turbulence increases the pressure difference required to create flow (less flow at the same pressure difference as laminar flow)
Is flow greater in turbulent or laminar flow overall
Small amount bigger in turbulent
How laminar flow relates to vascular resistance
Lamina nearest wall doesnt move, next layer slides under if, velocity highest in center
Larger tubes have higher mean velocity (more things are further away from the wall)
How to calculate reynolds number
=
p density x d diameter x v velocity
__________________
N viscosity
In a bigger tube more likely it will be turbulent if ___ increasing. Higher ___ means less likely to be turbulent
Velocity
Viscosity
___ molecules are more likely to be turbulent
Bigger
Reynolds what= laminar flow, what = turbulent
<2000
> 2000
How driving pressure changes with low compliance
Need twice as much pressure, harder to fill when vessel doesn’t push away and make room
How to calculate compliance
Change in volume divided by change in pressure
What is elastance
How is compliance different
How hard something recoils after stretching
Compliance is how hard it is to inflate something
What wall of aorta does in systole and diastole
Systole distends
Diastole recoils
Do you want a fast or slow pulse wave and why
Want a slow one, means arteries are more compliant and dont shove all of blood in at once which is what non compliant vessels do
Vein and artery compliance comparison
Veins more compliant at low pressures, but at high pressures they are similar
What increasing pressure in smooth muscle does to compliance in vessel
Decreases it
How volume, pressure, compliance changes with age
Cant push same amount of volume with age, CO decreases because no place for left ventricle to put the blood. Higher pressure and less compliance
What happens to compliance as pressures increase
Flattens out, less compliant
How compliance affects pulse pressure
Higher compliance means lower pulse pressure
How heart rate affects pulse pressure
Peripheral resistance increases with what
Lower hr- higher pulse pressure, diastolic time longer
Higher hr- lower pulse pressure, more output.
Mean pressure increase
Tension in wall depends on what
Diameter. Bigger diameter means more tension, smaller means more flaccid
Tension = what
Pressure times radius
Transmural pressure is what
Pressure inside minus pressure outside
Wall thickness ___ with increasing radius
Decreases
What happens to wall in aneurysm
High bp leads to them which leads to bigger radius, wall thinner where stretched with greater tension
Why small vessels can handle thin wall
Radius small, tension low, pressure low
What is flicks law of diffusion
D (diffusion constant) Times A (area of diffusion) Times delta P (pressure difference between two sides) Divided by D (distance over which area occurs)
