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What is axial streaming?
Blood cells flowing in the middle of the vessel in laminar flow only
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What are the relationships between flow and pressure in laminar and turbulent flow?
- Laminar flow: flow = pressure
- Turbulent flow: flow = sqrt pressure
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What is the difference between flow and velocity? What are the units for both?
- Flow: volume of fluid per second (ml/s)
- Velocity: distance traveled per second (cm/s)
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What is the equation to calculate velocity in a vessel?
- Velocity = flow / cross sectional area
- v = Q/A
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Cross-sectional area is greatest for which vessels? Smallest for which vessels?
- Greatest for capillaries
- Smallest for arteries
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Velocity is greatest in which vessels? Smallest in which vessels?
- Greatest in arteries
- Smallest in capillaries
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What is driving pressure?
Pressure gradient that drives blood flow
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What is transmural pressure?
Pressure difference between inside and outside of vessel
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What is hydrostatic pressure?
Pressure in a column of fluid due to gravity
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Is pressure in the heart chambers constant?
No, cardiac cycle produces oscillations in pressure
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What is compliance?
Distensibility of the vessel
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How does compliance affect pressure?
- High compliance = smaller changes in pressure per changes in volume (veins)
- Low compliance = larger changes in pressure per changes in volume (arteries)
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Why does blood pressure increase as we age?
Arteries harden as we age and so compliance decreases (larger changes in pressure)
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Besides aged arteries, which arteries are less compliant?
Arteries with arteriosclerosis
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What is aortic stenosis? What does this cause?
- Aortic valve is narrowed
- Stroke volume and systolic pressure goes down
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What does arteriosclerosis do to blood pressure?
Increases it because less compliance
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How does a rigid aorta change its actions when compared to a healthy aorta?
Rigid aorta distends during systole like its supposed to, but does not recoil in diastole like it should
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What is the equation relating resistance, pressure, and flow?
- Flow = change in pressure / resistance
- Q = ∆P / R
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What is Poiseuille’s law (equation)?
- R = 8nL / π r4
- n = viscosity
- L = length
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__________________ in flow or __________________ in resistance increases pressure
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Which variable has the greatest effect on resistance?
Radius
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When resistances are arranged in parallel, the total resistance is ____________ than the resistance of each individual path
Less
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What is conductance?
Ability for fluid to flow
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What happens to total resistance if you remove a pathway in a parallel circuit?
Resistance increases
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When resistances are arranged in series, the total resistance is ____________ than the resistance of each individual path
More
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