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32 Cards in this Set
- Front
- Back
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How is flow related to radius?
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From Pouisielle's law, we saw that R=1/r^4. B/c Q=P/R, we can say that Q = r^4.
Thus, they are directly related. |
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At what range of pressure does autoregulation work?
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50-160mmHg
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T/F:
Autoregulation if dependent on sympathetic innervation. |
False:
Autoregulation is an intrinsic property and independent of hormones and innervation. |
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What is the main goal of autoregulation?
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To hold flow constant in the face of changing pressure.
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How is myogenic tone induced?
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Increased pressure causes increased activation of stretch receptors. This causes depolarization and thus contraction.
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How does increasing myogenic tone affect flow?
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Flow is reduced. Increased tone increases resistance.
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Where does the myogenic tone mechanism take place?
In what kind of vessels? |
Resistance vessels only - not in pulmonary or veinous circulation.
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What two factors determine the concentration of breakdown products in interstitial fluid?
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*metabolic rate of cells
*rate of "wash out" |
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Name three breakdown products that can act as vasodilators.
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*adenosine
*H+ *CO2 |
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How can the metabolic mechanism compensate for an increase in MAP?
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There will be increased washout of vasodilators, thus the vessels will constrict and increase resistance to keep flow down.
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How could the metabolic mechanism compensate for reduced MAP?
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There would be less flow, and thus less washout of vasodilators which would then accumulate and cause dilation. This reduces resistance and keeps flow from dropping.
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How can an increase in metabolic rate result in an increase in O2 delivery?
What's another name for this? |
There would be a higher concentration of vasodilating breakdown pdts and thus vasodilation. This would decrease resistance and increase flow and delivery of O2.
Exercise hyperemia. |
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What's the fundamental difference btwn autoregulation and metabolic regulation?
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*autoreg seeks to maintain constant flow
*metabolic reg seeks to change flow to meet tissue demands |
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What are autocoids?
What are some examples? |
Local tissue factors that are vasoactive. They are produced, act, and are degraded locally.
*NO, histamine |
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What is the action of NO?
How can it be reduced temporarily and permanently? |
*vasodilation
*increased fat intake temporarily reduces *irreversibly falls with age |
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What is the action of angiotensin II and vasopressin on vessel tone? What are their effects on volume?
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They both cause vasoconstriction in the resistance vessels. They stimulate retention in the kidney and thus increase volume.
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T/F:
Neural and hormonal mechanisms affect the venous and pulmonary circulation as well as arterial. |
True.
However, most intrinsic mechanisms affect only the arterial and arteriolar side. |
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What's the fundamental difference between the extrinsic and intrinsic mechanisms microcirculation control?
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*extrinsic mechansims: seek to maintain constant MAP above all else
*intrinsic mechanisms: seek to maintain constant flow in tissue above all else |
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Which is stronger in skin circulation - intrinsic or extrinsic mechanisms?
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Extrinsic - there is little metabolic activity here, thus little intrinsic control.
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Which plays a bigger role in circulation to the cerebrum - intrinsic or extrinsic mechanisms?
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Intrinsic: autocoid and metabolic vasodilation will quickly cancel any sympathetic constriction.
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What is the simplified Starling equation?
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CFR = Kf (Pc - COPp)
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What does the constant Kf represent in the Starling equation?
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*permeability of capillary wall to water
*the surface area over which filtration can occur |
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What does plasma hydrostatic pressure favor - filtration or absorption?
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Filtration - movement out of the capillaries.
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What does colloid osmotic pressure favor - filtration or resorption?
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Resorption - the movement of fluid into the vasculature.
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How might increased arteriolar resistance affect CFR? (There are 2 reasons)
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This would reduce pressure in the capillary and thus reduce CFR.
Also fewer beds would be open and thus surface area for filtration (Kf) decreases. |
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How might decreased arteriolar constriction affect CFR? There are 2 reasons.
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It would increase b/c more capillaries would open thus increasing the surface area available for filtration (Kf).
Also pressure in the capillaries (Pc) would increase. |
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How would increased CVP affect CFR?
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Increased CVP would cause increased capillary pressure (Pc) and thus increased CFR.
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There are two ways histamine contributes to edema - what are they?
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*local vasodilator increases cap. P which increases CFR
*increases cap. permeability (Kf) which increases CFR |
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What is the major determinant of ultrafiltration?
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Cap. hydrostatic pressure in more important than COPp or wall permeability.
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Why is MAP less important than CVP in determining capillary hydrostatic pressure?
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Myogenic autoregulation usually negates any changes in MAP.
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How does dehydration affect CFR?
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It raises the COPp, which decreases (Pc - COPp). This decreases CFR and resorption is favored.
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How does hypoproteinemia affect CFR?
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COPp decreases, so (Pc-COPp) is greater. CFR increases and filtration is favored.
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