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Old 03-09-2012
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Kidney Sympathetic effect on kidney

I am not quiet understanding this concept.

I learned that with afferent constriction there is a decreases in GFR and and decrease in RPF therefore no effect on the FF since both decrease
but when it comes to sympathetic, there is afferent constriction as well due to it being more dominantly affected therefore there is a decrease in GFR and RPF but why in this case FF increase?

in both cases the afferent arteriole constricted but what makes a change in FF in sympathetic vs. afferent constriction without anything?

thank you
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Old 03-09-2012
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errr..doesnt sympathetic cause efferent arteriole constriction? (thru R-A-A)?
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Old 03-09-2012
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Sympathetic stimulation through its direct effect causes no change in ff


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Old 03-09-2012
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Quote:
Originally Posted by soodee View Post
I am not quiet understanding this concept.

I learned that with afferent constriction there is a decreases in GFR and and decrease in RPF therefore no effect on the FF since both decrease
but when it comes to sympathetic, there is afferent constriction as well due to it being more dominantly affected therefore there is a decrease in GFR and RPF but why in this case FF increase?

in both cases the afferent arteriole constricted but what makes a change in FF in sympathetic vs. afferent constriction without anything?

thank you

When just the afferent arteriole is constricted, the RPF dec., the GFR dec and FF has a TENDENCY to rise. However, it maybe normal, high or low depending on the DEGREE of constriction.

Under sympathetic stimulation, on the other hand, since there is predominantly afferent arteriole constriction, RPF dec., GFR dec., and FF RISES..!

Hope it is clear. Dr. Dunn explains it very well.
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Old 03-10-2012
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Quote:
Originally Posted by vna.rao22 View Post
errr..doesnt sympathetic cause efferent arteriole constriction? (thru R-A-A)?

--yeaa, it does,through the R-A-A, your right. As soon as their is a decrease in blood flow to the kidneys, during sympathetic. Kidneys should continue to filter blood to keep glomerular blood pressure up. To do this, angiotensin II constricts efferent arterioles, causing blood to build up in the glomerulus, increasing glomerular pressure and maintaing glomerular filtration rate.
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Old 03-10-2012
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I once read on some book that sympathetic system causes constriction on the afferent arterioles of the kidney therefore increasing the speed of blood which flows in that afferent arterioles and, eventually these accelerated blood will hit harder to glomerulus causing more blood to infiltrate through glomerular filtration barrier and causing FF to increase.
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Default FF

Quote:
Originally Posted by DR.PRO View Post
When just the afferent arteriole is constricted, the RPF dec., the GFR dec and FF has a TENDENCY to rise. However, it maybe normal, high or low depending on the DEGREE of constriction.

Under sympathetic stimulation, on the other hand, since there is predominantly afferent arteriole constriction, RPF dec., GFR dec., and FF RISES..!

Hope it is clear. Dr. Dunn explains it very well.
Its the same thing - just afferent arteriole constrcition, no matter what cause of it... And stil ldidnt get, why does only sympathetic increase FF?? when in FA is written that there is NO CHANGE.

Explain me please
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