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1.-Which curve describes the inulin profile along the nephron?
2.-Which curve describes the alanine profile along the nephron?
3.-Which curve describes the para-aminohippuric acid profile along the nephron?
Love your questions!

This one is sort of difficult to understand.. I think by anything higher than 100% it means completely reabsorbed, if so:

1. A (completely eliminated)
2. B (I guess it is completely reabsorbed?)
3. D (Same as RPF)
 

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What this graph is supposed to show is -- the concentration of the substances along the renal tubules.

As we go along the renal tubules, more water is reabsorbed- most of the Na and H2O in the PCT.

C- would be all the anions because the concentrations along the tubule does not increase because they get resorbed (most of them) early in the PCT- a little bit of K is also resorbed in the DCT so that would be a little higher than sodium.

Inulin- This man goes straight through the tubule without getting resorbed or secreted- however, since the water is resorbed as we go down in tubule-- it becomes more and more concentrated until it is finally put away in the urine

PAH -- this guy goes straight throught without being resorbed BUT-- he is also secreted in the PCT - which is why you will usually see this line a little higher than that of inulin -- because of the secretion which adds to its concentration-- after the secretion- the PAH goes straight through and is excreted in the urine-- but as the water gets resorbed, its concentration increases as we go down to pee. :p

All amino acids - including alanine are mostly resorbed in the PCT- just like glucose with the cotransporters(Na) - but their resorbtion is way greater than that of the ions in the PCT-so taken away in the PCT. Our body doesnt like to lose the amino acids or glucose. If you see glucose would indicate diabeties beyond a threshold(300-350) and if u see Amino acids in the urine means that we have big problems-- leading to albuminuria(minimal change disease because of losss of positive charge from the cations)--- anyway so the point is, most of it HAS to be resorbed in the PCT- thats why you see that steep drop in the beginning of the graph, which means that its concentration will not increase throughtout the tubule since it has already been resorbed.

Thats why I think the ans is DBD....and if we had the actual graph, PAH would be slightly higher than inulin, because of its secretion property
 

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i think its
C
A
D
inulin will not absorb and secreted so all inlulin will remain constant and excreted in urine so i select C
B : is also secreted from the kidney and so its conc is higher than inulin
A : most of the AA is reabsorbed and not present in urine so option A for AA
 

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Inulin is best for GFR measurement as its neither reabs nor secreted, so the amount filtered is the amount remaining (percentage filtered load remaining) - So that would be C.

Alanine is an AA, there are 3 carrier mediated AA reabsorption mechanisms along the PCT, so it would be reabs there more or less. im thinking more towards B perhaps.

and PAH will be a measure of the Renal plasma flow. its secreted along the nephron (so it gives a measure of the filtered amount and the remaining amount going through the vasa recta) so that has got to be above inulin which would be D
 

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Discussion Starter · #11 ·
correct answer

1.-Which curve describes the inulin profile along the nephron?
Curve C


Once Inulin is filtered, it´s neither reabsorbed nor secreted. Thus, 100% of the filtered inulin remains in tubular fluid at each nephron site and in the final urine

2.-Which curve describes the alanine profile along the nephron?
Curve A


Alanine, like glucose, is avidly reabsorbed in the early proximal tubule by a Na+-amino acid cotransporter. Thus, the percentage of the filtered load of alanine remaining in the tubular fluid declines rapidly along the proximal tubule as alanine is reabsorbed into the blood (remember Fanconi's syndrome!!!)

3.-Which curve describes the para-aminohippuric acid profile along the nephron?
Curve D


PAH is an organic acid that is filtered and subsequently secreted by the proximal tubule. The secretion process adds PAH to the tubular fluid; therefore, the amount that is present at the end of the proximal tubule is greater than the amount that was present in Bowman´s space.
 

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bebix wait a minute...

If you check page 218 of kaplan you will see that the answers you gave are actually for the clearance plasma concentration versus clearance not for TF/P

But your graph labels the in terms of TF/P....

Kaplan does not give a graph for TF/P. Check First Aid 2010 page 460 and read their explanation. Also UW has a question on it ... so those two graphs are completely different..

Edit- Just found the kaplan reference so I hope this helps-- Also check pg 223 Kaplan, under the concentration along the nephron-- "Because water is resorbed but not inulin, the concentration of inulin increases throughout the nephron. The greater the water resoprtion, the greater the inulin concentration. The segment of the nephron with the highest concentration of inulin is the terminal collecting duct".
So this line should be a increasing slope indicating an increase in concentration.. The reason Kaplan shows only the PCT, is because thats where the majority of water is resorbed, but if you check FA graph.. it shows it all along the nephron.,.

This is how they trick us we gotta catch it ;)
 

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Discussion Starter · #15 ·
bebix wait a minute...

If you check page 218 of kaplan you will see that the answers you gave are actually for the clearance plasma concentration versus clearance not for TF/P

But your graph labels the in terms of TF/P....

Kaplan does not give a graph for TF/P. Check First Aid 2010 page 460 and read their explanation. Also UW has a question on it ... so those two graphs are completely different..

This is how they trick us we gotta catch it ;)
This is NOT TF/P graph!!! (#5 @ IKR123 uploaded a TF/P graph and in my response to him I said that that particular graph was the TF/P graph of the proximal tubule)

btw,
"Kaplan does not give a graph for TF/P"...check p.223 :happy:
 

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This is NOT TF/P graph!!! (#5 @ IKR123 uploaded a TF/P graph and in my response to him I said that that particular graph was the TF/P graph of the proximal tubule)

btw,
"Kaplan does not give a graph for TF/P"...check p.223 :happy:
Yes.. I referenced that- I meant one that shows the complete nephron.

Actually... it is another way of representing a TF/P

Percent Filtered Load remaning = Filtered load remaining in the tubule after the resorption of water occurs /The total volume filtered x 100
= in other words = concentration of the fluid in the tubule after filtration/ concentration of the total plasma
= in other words = TF/P

If you see the clearance curve on page 218 it has 100 percent inulin clearance= ie everything that is filtered is excreted.. thats the only situation inulin will be a straight line when we are not going along the entire nephron(which we are in this question).

As for the question at hand, if you graph the points on going further from BC to DCT-- there is no way the concentration of inulin will remain the same, unless you have a nephron that does not resorb water

Anyways, thats just my take on it based on UW..
 

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Discussion Starter · #18 ·
Yes.. I referenced that- I meant one that shows the complete nephron.

Actually... it is another way of representing a TF/P

Percent Filtered Load remaning = Filtered load remaining in the tubule after the resorption of water occurs /The total volume filtered x 100
= in other words = concentration of the fluid in the tubule after filtration/ concentration of the total plasma
= in other words = TF/P

If you see the clearance curve on page 218 it has 100 percent inulin clearance= ie everything that is filtered is excreted.. thats the only situation inulin will be a straight line when we are not going along the entire nephron(which we are in this question).

As for the question at hand, if you graph the points on going further from BC to DCT-- there is no way the concentration of inulin will remain the same, unless you have a nephron that does not resorb water

Anyways, thats just my take on it based on UW..
Yes.. I referenced that- I meant one that shows the complete nephron.

Actually... it is another way of representing a TF/P

Percent Filtered Load remaning = Filtered load remaining in the tubule after the resorption of water occurs /The total volume filtered x 100
= in other words = concentration of the fluid in the tubule after filtration/ concentration of the total plasma
= in other words = TF/P

If you see the clearance curve on page 218 it has 100 percent inulin clearance= ie everything that is filtered is excreted.. thats the only situation inulin will be a straight line when we are not going along the entire nephron(which we are in this question).

As for the question at hand, if you graph the points on going further from BC to DCT-- there is no way the concentration of inulin will remain the same, unless you have a nephron that does not resorb water
we are just talking about % here... (this graph nothing have to do with water flow....if you want to talk about inulin and water, now you are talking TF/Posm)...remember, once Inulin is filtered, it´s neither reabsorbed nor secreted. Thus, 100% of the filtered inulin remains in tubular fluid at each nephron site and in the final urine.

btw, this question is from BRS Physiology by Costanzo...:happy:
 

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we are just talking about % here... (this graph nothing have to do with water flow....if you want to talk about inulin and water, now you are talking TF/Posm)...remember, once Inulin is filtered, it´s neither reabsorbed nor secreted. Thus, 100% of the filtered inulin remains in tubular fluid at each nephron site and in the final urine.

btw, this question is from BRS Physiology by Costanzo...:happy:
Which edition are you using? Mine doesnt have those answers? :eek:
Aren't we going through the entire nephron? Either I m totally confused or its a renal physio day for me..
 

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Discussion Starter · #20 ·
Which edition are you using? Mine doesnt have those answers? :eek:
Aren't we going through the entire nephron? Either I m totally confused or its a renal physio day for me..
5th edition (but it's also in the 4th edition)

btw, I found this really cool TF/Posm of the entire nephron (to nerdy?) :rolleyes:

this is from Guyton
Screen shot 2011-06-22 at 11.24.08 AM.png
click image to enlarge
 
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