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According to this:

The kidney contains afferent sensory nerve fibers that are located primarily in the renal pelvic wall where they sense stretch.

I think the stretch is due to urine. If I am correct then, I am unable to understand the following:

Stretch activation of these afferent sensory nerve fibers elicits an inhibitory renorenal reflex response wherein the contralateral kidney exhibits a compensatory natriuresis and diuresis due to diminished efferent renal sympathetic nerve activity. There is a negative feedback loop in which efferent renal sympathetic nerve activity facilitates increases in afferent renal nerve activity that in turn inhibit efferent renal sympathetic nerve activity so as to avoid excess renal sodium retention.

If I am correct , then how is renorenal reflex a negative feedback loop? Doesn't decreased efferent sympathetic activity increasing diuresis thus causing further increase in pressure in renal pelvis( contra lateral)?

Also how is sympathetic activity increasing renal pelvic pressure in the first place?

If I am wrong then, what is causing increase in renal pelvic pressure?


Support for my claim:

Hydronephrosis, a blockage of the outflow of urine or reverse flow of urine already in the bladder (called reflux) can cause the renal pelvis to become enlarged.

So, I think I am right in saying that urine increases pressure in renal pelvis, thus activating stretch receptors.

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  • $\begingroup$ Chapter 8 from the book Neural Control of Renal Function has all the explanations you need: ncbi.nlm.nih.gov/books/NBK57250 $\endgroup$ – user24284 Jul 19 '17 at 10:30
  • $\begingroup$ Unfortunately, I am still confused, please give a hint. $\endgroup$ – JM97 Jul 19 '17 at 12:20
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How is renorenal reflex a negative feedback loop?

You are confusing two different negative feedback loops.

1) There is a negative feedback loop in which efferent renal sympathetic nerve activity facilitates increases in afferent renal nerve activity that in turn inhibit efferent renal sympathetic nerve activity so as to avoid excess renal sodium retention.

This occurs on ipsilateral kidney only and is not renorenal reflex.

2) Stretch activation of these afferent sensory nerve fibers elicits an inhibitory renorenal reflex response wherein the contralateral kidney exhibits a compensatory natriuresis and diuresis due to diminished efferent renal sympathetic nerve activity. The renorenal reflex coordinates the excretory function of the two kidneys so as to facilitate homeostatic regulation of sodium and water balance. 

This is renorenal reflex, while it is negative feedback again, since reduced urine passage in one kidney paves way for other to increase urine passage/output.

Doesn't decreased efferent sympathetic activity increasing diuresis thus causing further increase in pressure in renal pelvis( contra lateral)?

Contra lateral kidney is not having same renal obstruction as in ipsilateral(unless otherwise stated). So, diuresis leads to increased loss of loads of electrolytes and water, thus, reducing hypertension.

Also how is sympathetic activity increasing renal pelvic pressure in the first place? If I am wrong then, what is causing increase in renal pelvic pressure?

Sympathetic activity is not increasing renal pelvic pressure here. Increased renal pelvic pressure was caused by obstruction to urine flow, eg. ureteral caliculi. Due to this obstruction urine could not pass from pelvis to bladder which increase pelvic pressure.

Contrarily, increased sympathetic activity in ipsilateral kidney tends to reduce pelvic pressure by reducing GFR. In contralateral kidney, decreased sympathetic activity will cause increased diuresis and reduced tension on diseased kidney for urine output.

Note: Increased GFR here, as a result of decreased symp supply, does not cause increased renal pelvic pressure since urinary passage is clear and not obstructed.

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  • $\begingroup$ No, I don't no how is sympathetic activity increasing pressure in renal pelvis, asaik sympathetic activity will reduce gfr so reduced pressure in the renal pelvis. $\endgroup$ – JM97 Jul 23 '17 at 1:19
  • $\begingroup$ Refer to edited answer. $\endgroup$ – Anubhav Goel Jul 23 '17 at 8:46

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