Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
38 Cards in this Set
- Front
- Back
|
What is laminar flow?
Where is it fastest? Slowest? |
*Fluid moving with a parabolic front.
*It is fastest at the center *it is slowest at the edges |
|
|
Pouisielle's law can be reduced to an expression of R and radius. How are these two related?
What does this insinuate? |
*R = 1/r^4
*that radius is the primary determinant of resistance |
|
|
What keeps changes in capillary bed resistance from having drastic effects on MAP?
|
The fact that most beds are arranged in parallel circuits buffers the effects on MAP.
|
|
|
What effects will dilation of a capillary bed have?
|
Lower R and increased Q and P in that capillary, but small effects system-wide.
|
|
|
What effects will constriction of a capillary bed have?
|
*increased R and decreased Q and P in the capillary bed
*buffered effects systemwide |
|
|
What is the equation for velocity of blood?
|
v = Q/cross-sectional area
|
|
|
What happens in a transition from a smaller vessel to a larger vessel?
|
Velocity drops, which can result in pooling and increased pressure on the vessel walls.
|
|
|
Why is velocity slowest in the capillaries?
What beneficial effect does this have? |
*Because the total cross-sectional area of the entire bed is taken into account.
*Slow velocity allows good exchange with tissues |
|
|
In words, how is tension defined by the LaPlace relationship.
|
Tension is the force a wall must generate to counteract the pressure inside.
|
|
|
What is the equation for tension?
|
T = Pr/h
*h = wall thickness |
|
|
What happens to tension in the event of an aneurysm?
|
The radius of the vessel inceases, thus tension increases.
|
|
|
In arteries, there is both high pressure and a large radius. How do these vessels prevent a high tension?
|
By their thick walls (high "h").
|
|
|
How do capillaries withstand pressures up to 100mmHg?
|
The radius is very small, this reduces tension and also allows the capillaries to have very thin walls.
|
|
|
In HTN, pressure in the arteries increases greatly. How do the arteries compensate?
|
There is hypertrophy of the wall and an increase in "h" - this reduces the tension on the artery.
|
|
|
In aortic regurgitation, blood flows back into the LV and increases LVEDP. How is this exacerbated by the LV? How is it compensated for?
|
A stretching or dilation of the LV increases "r" and thus increases T even more. The LV compensates through hypertrophy of the walls.
|
|
|
What effect would a LV MI have on the tension in that area?
|
The loss of myocytes would cause an aneurysm, thus increasing "r" and tension in that area. The risk for rupture increases.
|
|
|
Define diastolic wall tension (as experienced by the LV).
|
The distending force that must be overcome by contraction of the myocytes in order to compress the LV.
|
|
|
What is atherosclerosis? What effects does it have on systolic pressure? Why?
|
*stiffening of arterial walls
*increases systolic pressure *vessels are less able to stretch and recoil |
|
|
What is pulse pressure?
|
PP = systolic P - diastolic P
|
|
|
Name 3 determinants of systolic arterial P. How is each related to P?
|
*SV, directly related
*diastolic P, which determines the starting P *CPL, inversely related |
|
|
How would an inotropic rx affect systolic and diastolic arterial P?
|
*would increase SV (thru CTY)
*large rise in systolic P *modest rise in diastolic P |
|
|
What are the three main determinants of diastolic arterial P?
How is each related to P? |
*SVR, directly related
*systolic P, determines starting P *HR, directly related - determines time for draining before next surge in P |
|
|
What happens to pulse pressure when SVR decreases?
|
It increases. Decreased SVR means diastolic arterial P drops, but systolic pressure remains unchanged.
|
|
|
What happens to pulse pressure when SV increases?
|
It increases. Increased SV causes an lg increase in systolic arterial P, but only a modest increase in diastolic P.
|
|
|
How would tx with an arteriolar vasoconstrictor affect pulse pressure?
|
It would decrease. SVR increases, thus so does diastolic arterial P. Systolic P inceases only modestly.
|
|
|
What are two synonyms for CPL?
How can it be defined? |
Distensibility or capitance.
The change in volume for a given change in pressure. |
|
|
What is the equation for CPL?
|
CPL = delta V/delta P
(the change in volume for a given change in pressure) |
|
|
Which have greater CPL - veins or arteries?
|
Veins - they are elliptical and not totally filled.
|
|
|
What 2 things are the main determinants of CPL?
|
Passive structural components and active vascular smooth muscle.
|
|
|
How does contraction of VSM affect large arteries and veins?
|
It stiffens walls, but normally does not decrease diameter.
|
|
|
How does sympathetic excitation of veinous smooth muscle maintain SV?
|
It decreases CPL, which maintains or increases veinous return to the heart.
|
|
|
List the 6 main determinants of CVP.
|
1.Constriction of venules and sm. veins
2.decreased CPL in lg veins 3.Total blood vol. 4.Gravity 5.Capillary P. 6.CO |
|
|
How does gravity affect arterial pressure below and above the heart?
|
*Below the heart, G can add 90mmHg of P
*above the heart, G can subtract 30mmHg |
|
|
Which is affected more by gravity, venous or arterial circulation?
Why? |
Venous - b/c of the greater distensibility of the vessels.
|
|
|
What are 4 mechanisms venous circulation uses to counteract the effect of gravity?
|
1.Contriction of VSM reduces CPL
2.Increase arterial pressure 3.Skeletal muscle compression 4.movement of diaphragm |
|
|
How does decreased CPL affect CVP?
|
It increases it.
|
|
|
How will constriction of small veins and venules increase return to the heart?
There are 2 reasons. |
1.Increase CVP
2.Reduce to volume of the venous reservoir - i.e. mobilize more blood |
|
|
Why does a decrease in CO raise CVP?
|
Decreased CO creates a backlog effect that translates into greater CVP.
|
