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44 Cards in this Set
- Front
- Back
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Give an example of vessels in series? How is resistance calculated
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R vent, pulm a, lungs, pulm vein, L atrium, L Vent
Series resistances are the arrengement of vessels in an organ R= R1 + R2 + R3 etc ** flow is the same but pressure decreased as you get to the venous end |
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Give an example of vessels in parallel. How is resistance calc?
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Aorta, Brain, Coronary, Renal, GI, Hepatic etc. One vessel gives many branches
1/R= 1/R1 + 1/R2 + 1/R3 will decrease overall resistance blood flow to individual vascular beds is independently regulated |
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what is a benefit of A in parallel
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can adjust the portion of CO each vessle gets, blood flow can be independently adjusted in each vessel branch
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What are the different properties in A and V?
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Artery: more smooth mm, more elastic, deals with more pressure (stressed volume)
Vein: More collagen, valves, blood just hangs out (unstressed volume) |
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What is the relationship btwn velocity and vessel diameter/cross sectional area
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velocity is lowest in capilaries, small diameter & large Xsection area
velocity is highest in large diameter small x section area. aorta, vena cava |
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Why is it important to have elastic arteries?
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because they receive lots of pressure
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relative to area what portion of vessels contains the most blood
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veins
unstressed volume, huge resevoir for blood |
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what are 5 assumptions made about blood?
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1. closed system
2. non compresseble 3. heterogenous (non newtonian) 4. vessels are compliant, not rigid 5. always resistance to flow |
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Q=
v= |
Q= DP/R
v=Q/A |
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how is flow measured? whats its symbol? what is the formula
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ml/sec
Q= DP/R |
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how do velocity and flow differ?
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velocity is distance over time (cm/sec)
flow is volume over time (ml/sec) |
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we know how velocity changes with diameter, relate this to the equation for velocity
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v=Q/A
so as the area increases the velocity will decrease. Flow is constant Slow in capillaries |
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calculate area of a vessel
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pi r squared
**the diameter is the whole distance across the circle, the radius is half the diameter |
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Given Diameter and CO find velocity
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v=Q/A
v= CO/(pi r squared) |
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what does blood flow depend on?
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pressure gradient
resistance **an increase in pressure grad will increase flow and an increase in resistance will decrease flow Q=DP/R |
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Name those units!!!
Q v A DP R |
Q= ml/sec
v= cm/sec A= cm2 DP= mmHg R= mmHg/mL/min |
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when using the formula Q=DP/R what specifically is the R referring to?
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TPR
total preipheral resistance |
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Given Flow, Art Pressure and Venous Pressure determine vascular Resistance
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Q=DP/R
R= DP/Q (Artery P- Venous P)/Q |
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what is the driving force for blood flow?
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pressure gradients set up by vent contraction
**arteries can stretch during pressure and recoil during relaxation (compliance) |
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MAP=
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mean arterial pressure
mean pressure developed in 1 cardiac cycle Diastolic + 1/3 Pulse Pressure Pulse Pressue = Diastolic-Systolic |
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Formula for Pulse Pressure
What other formula uses pulse pressure |
PP= diastolic- systolic
MAP= Diastolic + 1/3 PP |
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whats more important in determing blood flow, pressure differnce or absolute pressure
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Pressure Difference
as the DP increases so will flow rate flow=Q=ml/sec |
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when resistance increases in a vessel what must happen in order to keep flow the same
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pressure difference must increase
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Vascular Resistance definition
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measure of hinderance to blood flow caused by friction btwn moving blood and vessel wall
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What will increase resistance?
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increased length
blood viscocity decreased radius series arrangement Radius is most influential R=1/r^4 |
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what will decrease resistance?
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increased radius
decreased viscosity decreased length parallel arrangement Radius is most influential R=1/r^4 |
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how are resistance and radius related
If radius doubles, resistance ______ and flow ________ |
R=1/r^4
decreases by 16, increases by 16 So if radius decreases by one half the resistance will increase 16 fold and flow decreases 16 fold |
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because the major component to resistance is __________, the ________ in _______ (vessel) are advantageous
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radius
smooth mm arteries |
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Normal flow is 300ml/min
occlusion is 45%, what is new flow? |
1/(.45 x .45 x. .45 x .45) = 24
so, R increases by 24 and flow is reduced by 24 (initial flow)(1/24) = new flow (300)(1/24) = 1 when the vessel diameter decreases the flow decreases |
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how will obesity affect resistance?
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obesity will increase vessel length
increased length increases R |
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as vessels are added in parallel what happens to the overall resistance?
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decreases!
now flow will increase |
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how does pregnancy affect resistance of blood flow? (placenta)
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decreases. the placenta is like adding another branch in parallel so overall resistance is decreased.
to compensate the body makes more RBC to increase the viscosity |
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Given Q and P find TRP for a bunch of vessels in parallel
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Q=DP/R
R=DP/Q then take 1/R = 1/R1 + 1/R2 etc |
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in laminar flow where is blood moving fastest? slowest?
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fluid on wall doesnt move
fluid in middle moves fastest **think of a river, flow is fastest in the center and slowest at the edges |
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what two flow patterns can occur in a tube?
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laminar: what we want
Turbulent: what we dont want |
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what determines if flow will be laminar or turbulent?
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renyolds number
when its less than 2000 its laminar, when its more than 3000 is turbulent |
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what factors contribute to renyolds number
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Rn= (density) (diameter) (velocity) /viscosity
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what sorts of things might make flow more turbulent
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increased density
increased diameter increased velocity |
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when blood flow is turbulent how is pressure and flow affected
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a larger pressure gradient is required to maintain flow
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compliance =
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compliance= DV/DP
c=ml/mmHg its the amt of volume a vessel can accept at a given pressure, the less pressure required to get more fluid into a vessel the more compliant it is |
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what does a high compliance indicate?
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a vessel can hold a large volume at a given volume
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what has a greater compliance an artery or a vein?
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vein (unstressed volume)
the arteries have lower compliance and have the stressed volume |
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compliance is decreased by what factors in the artery
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smooth mm
elastic properties |
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why does pressure decrease as you go from the aorta to IVC
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because resistance increases
Q= DP/R |
