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25 Cards in this Set
- Front
- Back
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What is the most important pressure in the pressure gradient (usually has amean of 70 to 100 mmHg)?
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Arterial pressure
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What is an apprxoimate range of mean arterial pressures?
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70-100 mmHg
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What is an approximate range of mean venous pressures?
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0-10 mmHg
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What determines blood flow?
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Pressure difference
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Give an equation for pressure different.
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Change in pressure = Blood flow x resistance (or Ohm's version V = IR)
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Describe the relationship between vessel radius and flow rate.
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It increases by the fourth power
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Describe the relationship between vessel length and flow rate.
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Flow rate is inversely related to vessel length
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List the four assumptions of the Poiseuille's equation.
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1. laminar flow 2. flow is through a smooth, cylindrical, rigid tube 3. steady, constant flow 4. Constant viscosity (or blood is a newtonian fuid)
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Which is more important in determing flow rate, pressure difference or absolute pressure?
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Pressure difference
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What is the effect on turbulence on efficiency and cardiac work?
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Turbulence is inefficient and makes the heart work harder
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What physical property of blood affects viscosity (hint: you can measure this)?
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Hematocrit
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When resistances are arranged in series total resistance is the ______ of individual resistances.
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Sum
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What are the two components of blood which contribute to its overall viscosity?
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plasma viscosity and cell viscosity.
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What is the approximate value of blood viscosity when compared with water's arbitrary value of 1?
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3.5
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Define: velocity profile is smooth and parabolic, and flow velocities are in the direction of net flow.
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Laminar flow
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Define: flow in which fluid components do not all move along the net axis of flow.
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Turbulence
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Where does laminar flow occur in the cardiovascular system?
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It occurs in most of the cardiovascular system of healthy individuals
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Where does turbulence occur in a normal healthy individual?
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Around the aortic valve; this is primarily due to the velocity of the flow around the aorta being high.
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What are the three major components of vascular resistance?
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Viscosity, radius (to the fourth power), and vessel length
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Where are vascular circuits arranged in series found (2)?
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GI and kidney
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True/False: most of the cardiovascular system is a parallel arrangement of resistances.
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TRUE
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How are parallel resistance elements summed?
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The reciprocal of each resistance is added and then this sum = 1/total resistance
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Define: systolic pressure - diastolic pressure
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Pulse pressure
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How do changes in vascular resistance affect pulse pressure?
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Increases in vascular pressure will decrease pulse pressure assuming all others variables stay the same (this is due to a rise in diastolic pressure)
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How do changes in heart rate affect pulse pressure?
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With an increase in heart rate, more blood per time will be ejected (assuming adequate filling) resulting in an increase in pulse pressure.
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