sympathetic stimulation -effect on gfr

[sania]

can somebody explain. that when kidney is symaptheically stimulated,vaso constriction of afferent and effernt arteioles will occur ,but constriction of afferent decreases the gfr and constriction of effernt increases the gfr,


IF A QUESTION COMES ABOUT SYMAPTHETIC STIMULATION, WHAT WILL U CHOOSE INCREASE THE GRF OR DECREASE THE GFR??


AS IN THIS QUESTION:_
all of the following will cause increase in gfr except;-

1)constriction of efferent areteiole.
2)decreasing plasma proteins
3)decreasing renin levels
4)dilatation of afferent arterole
5)inhibtion of symapthetic stimulation

ans is 3) ,understood that but if symapthetic stimulation is inhibted, no vasoconstriction of efferent ,so how is there increase in gfr?

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[Streetwolf]

I don't remember the specifics on which arteriole constricts and whatnot, but if you were in a fight/flight situation and your sympathetics were going nuts, you probably wouldn't want to be worrying about filtering your blood. It makes sense that the body would divert its energy to more important things for the time being.

 

[jswizdent]

Inhibition of the sym. nervous system causes afferent arterioles to be dilated increasing the flow in the glomerulus thus increasing gfr.

 

[chipotle]

can somebody explain. that when kidney is symaptheically stimulated,vaso constriction of afferent and effernt arteioles will occur ,but constriction of afferent decreases the gfr and constriction of effernt increases the gfr,


IF A QUESTION COMES ABOUT SYMAPTHETIC STIMULATION, WHAT WILL U CHOOSE INCREASE THE GRF OR DECREASE THE GFR??


AS IN THIS QUESTION:_
all of the following will cause increase in gfr except;-

1)constriction of efferent areteiole.
2)decreasing plasma proteins
3)decreasing renin levels
4)dilatation of afferent arterole
5)inhibtion of symapthetic stimulation

ans is 3) ,understood that but if symapthetic stimulation is inhibted, no vasoconstriction of efferent ,so how is there increase in gfr?

effect of renal blood flow on GFR
• increased RBF —> reduce tendency of rising glomerular COP to resist filtration through glomerulus —> increased GFR
[is this the rationale for flow, not pressure being important in maintaining urine production?]

b) effect of afferent arteriolar constriction on GFR
• afferent arteriolar constriction —> decrease RBF & decrease glomerular pressure —> decreased GFR

c) effect of efferent arteriolar constriction on GFR
• efferent arteriolar constriction —> increased resistance to outflow from glomeruli:
i) —> increased glomerular pressure —> increased GFR
ii)—> decreased RBF —> increased glomerular COP —> decreased GFR
‑> net effect ?

e) effect of sympathetic stimulation on GFR
• sympathetic stimulation —> preferential afferent arteriolar constriction —> decrease RBF & decrease glomerular pressure —> decreased GFR

f) effect of arterial BP on GFR
• Increased BP —> automatic afferent arteriolar constriction [autoregulation]:
i) —> decrease RBF —> decreased GFR
ii)—> attenuated increase in glomerular pressure
è slight increase in GFR —> large increase in urine production