Flashcards in Renal blood flow Deck (25)
What is the term used to describe the proportion of fluid that passes into the renal tubules as compared with the total amount of fluid that is sent to the kidney.
What is the formula for FF?
GFR/RPF = FF
What is a typical filtration fraction for a healthy person?
What do diuretics do to the filtration fraction?
They decrease the filtration fraction
What happens if the kidneys are not being perfused adequately?
Kidneys will compensate by increasing the filtration fraction
How do the kidneys alter the filtration fraction?
By constricting/dilating the afferent and efferent arterioles depending on the situation
If changes only occur in the _____________ arteriole, then FF is NOT altered.
True or False: Any change in the efferent arteriolar resistance WILL alter the FF.
There is an increased resistance in the efferent arteriole. What happens to the RBF? GFR?
RBF: decreased. GFR: increased
There is an increased resistance in the afferent arteriole. What happens to the RBF? GFR?
RBF: decreased. GFR: decreased
There is a decreased resistance in the efferent arteriole. What happens to the RBF? GFR?
RBF: increased GFR: decreased
There is a decreased resistance in the afferent arteriole. What happens to the RBF? GFR?
RBF: increased GFR: increased
What factors control the afferent and efferent arterioles?
1) Sympathetic NS (NE causes universal constriction)
2) AT2 (universal constriction
Where is renin produced?
Granular cells of the afferent arteriole
What 5 factors mediate release of renin?
1) sympathetic NS (direct infusion of Ne/E, stimulates)
2) baroreceptors (decreased stretch stimulates)
3) Prostaglandins (production stimulates)
4) Macula Densa (decreased NaCl stimulates)
5) AT2 (receptors on granular cells inhibit renin as negative feedback loop)
Nitric Oxide is a powerful vasodilator in the kidney. It is very sensitive to inhibition by even low doses of ______________
Your kidneys want to have the same amount of perfusion all the time, no matter what the body is doing systemically. So if there was a systemic decrease in the MAP, what would the kidneys have to do to maintain steady blood flow?
(This is the whole idea of autoregulation)
What is Laplace's Law?
Wall tension = transmural pressure x lumen radius
The kidneys want to maintain a constant wall tension. So if there was an increase in the MAP (transmural pressure), what would the kidneys do to compensate?
Decrease the lumen radius
Put simply, to maintain renal blood flow during elevation in systemic pressure, what happens to the renal vessels?
They constrict to increase resistance.
Autoregulation is also achieved via the macula densa cells. Explain.
Macula densa cells (in JGA) detect changes in NaCl concentration. These cells send a signal that increases or decreases afferent arteriolar resistance accordingly.
(In addition to the role they play with Renin)
What is the purpose of renal autoregulation?
To preserve solute and water balance during rapid changes in perfusion pressure that occur frequently throughout the day.
I think he's pretty excited about the concept of renal clearance. What's the magic formula?
(Urine concentration x flow rate)/Plasma concentration = clearance.
(based on the principle of conservation of mass: renal input(x) = renal output(x))
_____________ is a diagnostic agent useful in medical tests involving the kidney used in the measurement of renal plasma flow