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81 Cards in this Set
- Front
- Back
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Power is
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the rate energy is transferred. describes how fast work is being done
Watts=Joules/sec |
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Work is
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the amount of energy that is transferred, integrates total power used to complete job over time
Work = avg power x total time Joules= Joules/ sec x seconds |
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Energy
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has multiple physical forms such as
potential kinetic heat radiation units vary on which type of energy used |
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conservation of energy
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fundamental law stating that energy is never lost, only converted to another form
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potential energy is
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energy that is stored and can be converted to another form of energy
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kinetic energy is
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energy in motion and is proportional to the velocity squared of the movement
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pressure is
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the measure of force per unit of area
two categories: Static pressure (potential energy) Dynamic pressure (kinetic energy) |
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flow (volumetric) is
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the volume of fluid per time that moves past a point
liters/min meters cubed/sec |
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resistance is
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the ratio of pressure drop across a flow path per volumetric flow
measure of the impediment which is overcome for flow to occur |
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capacitance is
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the measure of the ability to hold a change in volume per change in time
change in V / change in t |
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compliance is
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the ratio of the change in volume to a change in pressure
dV/dP |
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Velocity is
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the speed that a fluid moves in a specific direction
units of distance/time m/sec cm/sec |
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viscosity (fluid) is
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the ratio of shear stress to the shear rate of a fluid
measure of the resistance of a fluid to flow due to the attraction of molecules |
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In hemodynamics the driving force that propels blood is a
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change in energy
it travels from areas of high energy to those of low energy |
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when considering the law of conservation energy can be divided into two categories of
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potential and kinetic energy
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The law of conservation makes it so that there is only a conversion back and forth between
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kinetic and potential energies
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the pressure that represents the force exerted on the vessel walls represents
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potential energy
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the force in the direction of flow represents .... which is related to the velocity of the blood
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kinetic energy
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hydrostatic pressure is
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potential energy related to the weight of a column of fluid above a reference point secondary to gravity
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the equation for hydrostatic pressure is
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ro x g x h
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in the hydrostatic pressure equation h means
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the height of the column
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in the hydrostatic pressure equation ro means
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density
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in the hydrostatic pressure equation g means
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gravity
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hydrostatic pressure is proportional to the
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height of the column, and density of the material
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clinically hydrostatic pressure is related to the ___ and ___ of the patient
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height, position
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what is the hydrostatic pressure in the body?
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2mmHg/inch
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In volumetric flow Q means
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volumetric flow
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in fluid dynamics v is
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velocity
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high flow does/ doesn't correlate to a high velocity
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doesn't
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High compliance infers that there is a large increase in ___ with small change in ___
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volume, pressure
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fluid viscosity is defined as
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the ratio of the shear stress to the shear rate
a measure of the resistance to flow offered by a fluid / molecule stickiness |
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fluid viscosity is ___ dependent
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heat
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resistance to flow is ___ to the viscosity of the fluid
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proportional
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for the same radius and the same volumetric flow, if the length increases the resistance ____
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increases
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resistance is ____ to length
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proportional
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resistance is ____ to 1/radius
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proportional
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for the same length, if the radius increases the resistance ___
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decreases
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which has a greater impact on resistance? length or radius
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radius
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resistance is ____ to 1/radius^4
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proportional
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a higher viscosity results in a ____ resistance to flow
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higher
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what is the resistance equation
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R = (8 x length x viscosity) / (pi x radius^4)
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for the same velocity a larger CSA ____ volumetric flow
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increases
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Q is ____ to area
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proportional
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area is equated as
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radius squared
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for the same CSA a higher average velocity ____ the volumetric flow
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increases
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Q is ____ mean spatial velocity
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proportional
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the contiunity equation states that
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flow through one region must equal all the other flow through any other reigion in the flow system
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what is the continuity equation
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Q = mean spatial velocity x area
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a v with a line over it represents
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mean spatial velocity
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change in P (pressure) is ____ to R (resistance)
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proportional
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the smaller radius of pipeline B results in a ____ pressure gradient for hte same volumetric lower as pipeline A
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higher
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change in pressure is ____ to Q
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proportional
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what is a Newtonian fluid
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the viscosity of the fluid only changes with temp
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is blood a newtonian fluid
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no
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What assumptions are made to us poiseuille's law
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flow conduit is a rigid cylindrical tube
flow is stead, stable, laminar flow fluid is newtonian |
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when is poiseuille's law applicable?
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when the hemodynamic state is such that error caused by incorrect assumptions is small enough that the law is good enough to predict behavior
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Bernoulli's equation says that
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for a closed loop system, all the energy at one point must equal all the energy at another point
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to use the simplified Bernoulli's equation we need to assume that
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blood is flowing through a rigid tube
blood is a non-viscous fluid no friction surface occurs blood is an incompressible homogenous fluid an blood is in laminar flow |
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steady flow is
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constant volumetric flow
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pulsatile flow is
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fluid which moves in a well behaved manner and uniform direction
will move in concentric rings not crossing boundaries |
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plug flow is
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a velocity profile that is relatively consistent across the vessel
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parabolic flow is
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a laminar flow profile which mimics a parabola
normal arterial blood flow in a straight, undiseased segment |
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disturbed flow
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any deviation from laminar flow
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turbulent flow is
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when fluid does not move in a well behaved manner
chaotic or random flow |
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acceleration is
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change of velocity over time
positive |
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entrance effect
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change in velocity profile which happens when entering a vessel of reduced diameter
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exit effect
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change in velocity profile which results when exiting from a vessel of smaller diameter
the inertial energy is dissipated by turbulent flow |
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Raynolds number is
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a dimensionless index that indicates the occurrence of turbulent flow
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the higher the reynolds number the ____ the likelihood of turbulence occuring
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greater
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reynolds number is a ratio between the ____ forces and the ____ forces
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inertial, viscous
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What is reynolds ratio
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R = intertial forces / viscous forces
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What is reynolds ratio equation
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R = (ro x d x v) / (nu)
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reynolds number when it is _______ usually results in turbulence
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>2000
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Explain the normal pressure waveform in the aorta
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a rapid systolic upstroke followed by a gradual decrease to the dicrotic (compliance) notch, followed by the gradual decline in pressure throughout diastole
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atheroscelrotic arteries will / will not have a dicrotic notch?
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will not
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capacitance allows energy to be stored in the walls of the aorta to provide
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energy to propel blood during diastole
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when pressure is applied to an elastic vessel wall, it stretches in a
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radial direction, causing an overall increase in CSA over the length of the vessel
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compliant vessels cause a fallacy in poiseuille's law assumption because
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the compliant vessels create a much faster increase in volume with respect to pressure than the law predicts, causing a non linear relationship change between pressure and volume
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how much blood is held in the venous system at rest?
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65%
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what allows for the venous system to act as a reservoir
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it's capacitance
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where does blood also reservoir at rest?
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skin and liver
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