USMLE Forum - Largest USMLE Community

Can anyone please explain 2nd q?


http://i.imgur.com/tai0BrA.jpg

GFR decreases
RPF decreases X 2
FF=GFR/RPF=Increases
--pt becomes hypovolemic-->Renal perfusion decreases
--Angiotensin II is released which causes vasoconstriction of efferent arteriole more than affrent arteriole. So GFR is decreased but not very much
--RPF decreases more both due to hypovolemia and angiotensin mediated vasoconstriction of afferent arteriole

Hope i answered ur question

Need help with Usmle step 1, usmle step 2CK or Usmle step 2CS exam preparation? PM skype id usmletutor3

In FA-2014-Pg526 says:

Angiotensin ll preferentially constricts efferent arteriole (decrease RPF, increase GFR, so FF increases)

im confused too now.

Correct that in FA

oh so that's wrong in FA...

Thanks for your explanation. I wonder if other info on that list is correct.

You got pat that hypovolemic ( ↓blood vol) im gone talk about few factor in order the fog would be clear for u. Just bear w me here you have pat again in simple term u know RBF reflexively related to systemic arterial P that been sad in pat initial phase of systemic arterial P ↓, you know your baroreceptors of carotic sinus & aortic arch kik in sympathy -> on Afferent -> ↓ perfusion in glomerular & GFR at least on side of our story to try ↑blood vol -> ↑BP.
You got ↓ BP alarm granular cells of Afferent arterioles JGA store to release Renin that triggered by the DEC to activate Ang -> AngI -> to last dest -> AngII-> Aldosterone, arteriolar vasoCon (inc BP), ADH, INC salt absorb -> all in all as big pic -> INC BP & INC Blood vol.
Keep this part of story
I want u to know the relationship not liner cross range of physio BP DUE TO AUTOREGULATION and that’s what u missing on your understanding and magic number u may want to take home here that work in pat and not fails autoregulation is systolic BP did not falls below 80. (remember if the 80 fails in me and u as healthy individual then u would have no luck on autoregulation scenario) I hope u not lost yet. So like everything in life there is limit to autoreg as well.
IN all is about how to maintained GFR norm.

So how the autoregulation works? 2 players
Myogenic reflex/response *contract or relax within Afferent -> dilation (low perfusion P) all like chain reaction that alarm wake tem ) intrarenal bios vasoDilator PG/prostacyclin &PGE2 kallikrein & kinins and NO response to low renal PP. (*we are interested on contract Ca influx through voltage gated on Afferent and inhibited by PG)
Tubuloglomerular/TGF feedback that again mech for autoreg ( can wake up in hypOtension, hypOvolemia like pat here or ↓Na @macula densa DT) -> via paracrine mech.
Again what factor INC sensitity of vol contraction TGF many namely PG, adenosine, thromboxane, ANG II…
What constrict Efferent? ANGII ( depend on Ca mobilization from internal stores and that’s why insensitive to CCB) and PG may counteract the constriction during vol contraction
Other word to maintained norm GFR u must inc vasodilatory PG on Afferent, and Efferent INC ANGII again in sene that DEC perfusion P.
Going back to beginning ↓MAP -> ↓RBF & GFR but u need to remember that will be narrow due to autoregulation I JUST dissected for you and u RBF & GFR change in the same direction ( GFR less than RBF due to again compensatory change in EFFERENT above also mention
Hypovolemic -> Constriction Afferent & Efferent -> more ↓↓ RPF & less ↓GFR this part is more at like math problem u want to remember
FF =↓ GFR/↓↓RPF like ↑FF= GFR/↓RPF

The FA 526 your confusion regard Efferent arteriole constriction not about pat here hypovolumic or factor that play on it as we just dissect as whole. Its info that if u constrict the efferent what would happen to FF=GFR/RPF in glomerular dynamics.

I hope that clear it up


I apologies behalf of the members who just post qs and never have exp/ans to back up the qs even after few days by. It seems the forum is playground for them. They think copy and paste is medicine

So you are saying FA is only talking about efferent constriction and in this patient the story is different since they are talking about hypovollumic person. It makes sense now. Thank you .


Cardio, you're the best!

You don't just post qs but you take time to explain everyone and respond to everyone and not leave them confused. I appreciate your help. Other are posting qs for their friends only as they only respond to them and not to other students.

Thanks again for your help. I have to go now.

@determined sorry for the inconvenience man but i did not see your post until now that too one of my friend alerted me about ur post..

@ irrespective of whether we Copy paste or type text..What is important is whether we have learned the concept or not.. plus someone really need to learn how to behave irrespective of whether learn medicine or not.. Anyway I don’t wanna say anything bad about anyone becos that is not my character plus im least bother and I don’t have time for all this nonsense..


Q1 Explaination

http://i.imgur.com/Y5vjFkb.jpg

http://i.imgur.com/RgHaSfI.jpg

Q2 Explaination

http://i.imgur.com/1wIrKaK.jpg


All the best determined)>>

http://i.imgur.com/ZLuI5Z2.jpg