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17 Cards in this Set
- Front
- Back
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Why is a pressure reference point necessary for measuring venous pressures?
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All pressures are relative to the atm. Because pressure is measured as the weight underneath a particular height of fluid, BP taken at the feet while standing will be higher than at the head. The pressure reference point gives an arbitrary point at which to take pressure for clinical purposes.
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What is another name for the primary reference point?
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phlebostatic axis
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Why is a pressure reference point important?
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Without a standard reference, central venous pressure measurements would be useless (how would you compare them?)
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How can central venous pressure be used clinically?
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Cardiac performance evaluation
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What is the function of venous valves?
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Prohibit the backflow of blood retuning to the heart and help propel the blood back to the heart (via extravascular compression of the veins)
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Define: the ability of the veins to accommodate a large volumetric change without a requiring a large change in pressure
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Compliance
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What is the amount of blood stored in the venous system?
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60-80%
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What is the function of compliance?
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To serve as a blood reservoir system for the cardiovascular system
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Define: the amount of blood remaining in the vascular systems at zero pressure
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unstressed vascular volume
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What two systems' pressures interplay to dictate the unstressed vascular volume?
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The amount of unstressed vascular volume is afunction of the state of tension of the vascular smooth muscle in the arteries and the veins.
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How does activation of the sympathetic nervous system reduce unstressed vascular volume?
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It constricts the vascular smooth muscle which increase the amount of pressure in the vein thereby reducing the unstressed vascular volume
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What are the two factors which alter unstressed vascular volume?
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change in Pressure (increase results in increase in) and change in volume (increase in results in increase in) in the venous system
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What occurs to increase the pressure when one stands from a reclining position?
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sympathetic nervous system causes veins to constrict to keep blood from pooling in the legs and feet
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Define: the pressure in the atrium at which venous return to the right atrium stops.
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mean systemic (circulatory) filling pressure
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How does normal human anatomy prevent venous pooling?
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Valves keep vein moving up (provided there is a pumping action)
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Describe the neuronal mechanism which helps prevent venous blood pooling.
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If blood pressure begins to drop to low, the sympathetic nervous system constricts the veins' smooth muscle which squeezes blood through the valves
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Describe the behavioral mechanism which helps prevent venous blood pooling.
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Wearing of compression socks, and movement keep blood moving upward
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