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Old 02-04-2012
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Kidney Sympathetic stimulation and the Filtration Fraction

I don't quite get this concept from Kaplan video - how sympathetic stimulation causes increased Filtration Fraction, if renal vascular constriction decreases both GFR and RPF

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it decreased RPF moreso than GFR. both are decreased but moreso RPF. therefore FF increases.

FF = GFR / RPF
ie. = 120/600 = 20%
after afferent constriction:
FF = 110/500 = 22%

RPF is solely dependent on the amount of blood coming in, whereas GFR is dependent on a few factors. Hence, RPF is decreased more than GFR is.

atleast thats how I think of it.
someone please do correct me if I'm wrong.
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Quote:
Originally Posted by khushi.chahal View Post
it decreased RPF moreso than GFR. both are decreased but moreso RPF. therefore FF increases.

FF = GFR / RPF
ie. = 120/600 = 20%
after afferent constriction:
FF = 110/500 = 22%

RPF is solely dependent on the amount of blood coming in, whereas GFR is dependent on a few factors. Hence, RPF is decreased more than GFR is.

atleast thats how I think of it.
someone please do correct me if I'm wrong.

in case of angiotensi II i understand that it causes constriction of efferent more than afferent therefore GC hydrostatic pressure increases with decreasing RPF - so there is increased FF
in sympathetic stimulation both afferent and efferent constrict that cause decrease in GC hydrostatic pressure which decrease GFR and with decreased RPF there shouldnot be increase in FF
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Originally Posted by MedicalExaminer View Post
in case of angiotensi II i understand that it causes constriction of efferent more than afferent therefore GC hydrostatic pressure increases with decreasing RPF - so there is increased FF
in sympathetic stimulation both afferent and efferent constrict that cause decrease in GC hydrostatic pressure which decrease GFR and with decreased RPF there shouldnot be increase in FF
i remember in Kaplan they told us that sympathetic stimulation affects the afferent moreso than the efferent.
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Quote:
Originally Posted by khushi.chahal View Post
i remember in Kaplan they told us that sympathetic stimulation affects the afferent moreso than the efferent.
Yes thats right
I found in brs physiology 5ed
FF doesn't change


Sympathetic stimulation and the Filtration Fraction-imageuploadedbytapatalk1328394740.945717.jpg
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