paganini
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A person is given a drug that dilates the afferent arteriole and constricts the efferent arteriole by the same amounts. Assuming no other actions of the drug, what happens to this person's GFR, RBF, and filtration fraction?
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| SILVER
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- GFR will increase
- RBF will increase
- FF will decrease slightly
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| new_n_lost
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GFR will increase
RBF will decrease
FF will increase.
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| SILVER
DoWhatYouGotToDo!
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on second thought, it should be
- GFR increase
- RBF decrease
- FF increase
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| paganini
Forum Senior
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RBF will show no change because the drug has no effect on total renal vascular resistance. GFR will increase because of a large increase in PGC. Filtration fraction will, therefore, increase. (Now back up and think a bit more about the GFR: Because filtration fraction increases, there will be a larger than average increase in oncoticGC along the glomeruli, and this will offset some of the GFR-increasing effect of the increased PGC, therefore, GFR will not increase as much proportionately as the PGC.)
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| drduck
Forum Guru
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GFR will increase
RBF will decrease
FF will increase
i dont agree with the concept of normal RBF on constr the efferent arteriole
plz some one help....
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| paganini
Forum Senior
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The RBF changes reflect changes in total renal arteriolar resistance, the location of the change being irrelevant. A change in arteriolar resistance produces the same effect on RBF regardless of whether it occurs in the afferent arteriole or efferent arteriole. Because these vessels are in series, a change in either one has the same effect on the total. When the 2 resistances both change in the same direction, the most common state of affairs, their effects on RBF will be additive. When they change in different directions, one resistance increasing and the other decreasing, they exert opposing effects on RBF.
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| samreena
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if the affrent in dilated ,that means more filteration rate ,
GFR =increases
the flow through out the kidney is decreased ..
RBF=decreases
fliteration fraction =GFR/RBF
so as the GFR increases and RBF is decresing ..the FF shud increase ..
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| ssrpk
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i agree with you paganini absolutely.
lets say afferent arteriolar radius is doubled, the resistance across this vessel will be decreased 4 times;and efferent arteriolar radius is halved, resistence across with vessel will be increased 4 times. Thus the net effect on total renal blood flow is zero.
interesting questions paganini 
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| tompat
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yeah the only thing remains unchanged is RBF, no doubt about that
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