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  #1  
Old 09-01-2011
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Help NBME 7 concept (spoiler)

Block 2, question 39

pre-experiment:
RBF is 200ml/min, Hto 40% and FF 25%

... most likely after infusion of angiotensin II for 60 minutes...

the correct answer is "Increased filtration fraction"...but, it seems like "Decreased renal blood flow" is also correct...
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  #2  
Old 09-01-2011
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how would it be decrease renal blood flow? im curious because i dont see how that works and i thought aspirin would do that. did u think it was that due to the vascons due to ATII?

it would seem that between increase FF and decrease RBF, increase FF is the better answer. ATII directly works on efferent arteriole constricting it and that increases GFR which increase FF.
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Old 09-01-2011
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Originally Posted by ujustgotdoctored View Post
how would it be decrease renal blood flow? im curious because i dont see how that works and i thought aspirin would do that. did u think it was that due to the vascons due to ATII?

it would seem that between increase FF and decrease RBF, increase FF is the better answer. ATII directly works on efferent arteriole constricting it and that increases GFR which increase FF.
yup, the correct answer is increase FF
but, if you constrict the EA, the RPF should also decrease...and since RBF = RPF / (1 - Hto)...RBF too?
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Old 09-01-2011
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Originally Posted by bebix View Post
yup, the correct answer is increase FF
but, if you constrict the EA, the RPF should also decrease...and since RBF = RPF / (1 - Hto)...RBF too?
yes AT2 cause decrease RPF increase GFR and so FF increases.
maybe and maybe! in first place before expirement the RBF was decreased . so now it can't decrease more!!! GFR is 30 at first place
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  #5  
Old 09-01-2011
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i see what ur saying. it just goes to wat u think is the best answer possible. hopefully we wont have too many of those on the real test
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Old 09-01-2011
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Quote:
Originally Posted by bebix View Post
Block 2, question 39

pre-experiment:
RBF is 200ml/min, Hto 40% and FF 25%

... most likely after infusion of angiotensin II for 60 minutes...

the correct answer is "Increased filtration fraction"...but, it seems like "Decreased renal blood flow" is also correct...
yeah i think u have done offline nbme 7 ? ... correct answer is decreased renal bloood flow ... and filtration fraction is sameee it doesnt change by angiotenion2 because it act as efferent arteriole causing constriction ..i was also shocked to c the answer but i was right .... i discussed with one of my friend also
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Old 09-01-2011
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Originally Posted by dr_lizard View Post
yes AT2 cause decrease RPF increase GFR and so FF increases.
maybe and maybe! in first place before expirement the RBF was decreased . so now it can't decrease more!!! GFR is 30 at first place
angiotensin 2 causes efferent arteriolar constriction decreasing renal blood flow and as we know increased glomerular hydrostatic pressure so GFR increases.... so formula of F.F is renal blood flow/GFR ... renal blood flow (numerator decreases)and GFR(denominator)increases so FILTRATIO FRACTION remains constant .....
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Old 09-01-2011
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Quote:
Originally Posted by yasirsattar75 View Post
angiotensin 2 causes efferent arteriolar constriction decreasing renal blood flow and as we know increased glomerular hydrostatic pressure so GFR increases.... so formula of F.F is renal blood flow/GFR ... renal blood flow (numerator decreases)and GFR(denominator)increases so FILTRATIO FRACTION remains constant .....
FF = GFR / RPF

1/FF = RPF / GFR

in the formula we use RPF and not RBF

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Old 09-01-2011
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Originally Posted by yasirsattar75 View Post
yeah i think u have done offline nbme 7 ? ... correct answer is decreased renal bloood flow ... and filtration fraction is sameee it doesnt change by angiotenion2 because it act as efferent arteriole causing constriction ..i was also shocked to c the answer but i was right .... i discussed with one of my friend also
sorry, but i did it online
I also have the offline version - the best way to check the right/wrong questions after you are done with the online part

btw, my answer was E) Decreased renal blood flow ---> wrong

Last edited by bebix; 09-01-2011 at 09:11 PM.
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  #10  
Old 09-02-2011
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I gave Form 7 online.
I had marked increase in FF because....

After angiotensin there is Efferent constriction
a)This leads to decrease Renal plasma flow ~ renal blood flow
b)Increase in GFR
So even though decreased renal blood flow is the right choice increased FF is more correct cause it takes into account both GFR and RBF.
Weird question though. I had marked the question for thorough review and spent a considerable amount of time deciding the answer choice.

What was your predicted score ?
Btw do u have the answer key for form 7.??
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Old 09-02-2011
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Originally Posted by mayursn39 View Post
I gave Form 7 online.
I had marked increase in FF because....

After angiotensin there is Efferent constriction
a)This leads to decrease Renal plasma flow ~ renal blood flow
b)Increase in GFR
So even though decreased renal blood flow is the right choice increased FF is more correct cause it takes into account both GFR and RBF.
Weird question though. I had marked the question for thorough review and spent a considerable amount of time deciding the answer choice.

What was your predicted score ?
Btw do u have the answer key for form 7.??
Hi...I think in the end FF answer is better than just RBF answer.

I got 240.

I dont have the answer key...I just took it yesterday ...I do remember my answers and I already checked the ones that I had it wrong.
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Old 09-02-2011
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Quote:
Originally Posted by bebix View Post
Hi...I think in the end FF answer is better than just RBF answer.
Exactly my point

Quote:
Originally Posted by bebix View Post
I got 240.
Wow even i had the same predicted score
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  #13  
Old 09-04-2011
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Just to add,

Kidney is one of the organs where blood flow is highly auto-regulated. So, infusion of angiotensin II will not have that significant effect.
Secondly we know that Angiotensin acts more on the efferent arteriole. So as a result the FF is increased after infusion of angiotensin.
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