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  1. #1
    QR93 is offline Newbie 510 points
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    Effrent arteriolar constriction & Pressure?

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    I've been told that constricting the efferent arteriole of the nephron will decrease the peritubular capillary pressure. I understand that it will increase GFR because there will be increased pressure downstream of the constriction and the difference between the wider afferent arteriole and now even more narrow effrent arteriole will be greater (I hope I'm correct anyway).

    What I don't understand is why/how the pressure in the peritubular capillaries would decrease? (if the efferent arteriole is constricted).


    Also, could someone please confirm that Angiotensin II constricts both the efferent and afferent arterioles, but has a greater effect on the efferent arteriole? And that the sympathetic system only contricts the afferent arteriole?

  2. #2
    valenselv is offline Newbie 510 points
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    You have to have in mind that the efferent arteriole is followed by the peritubular capillaries, so if you constrict upstream of the capillaries (you increase the resistance imposed to the flow), you can only have a drop on the pressure. It's the opposite of what happens upstream of the effrent arteriole (which is what I think you meant to say with this
    I understand that it will increase GFR because there will be increased pressure downstream of the constriction and the difference between the wider afferent arteriole and now even more narrow effrent arteriole will be greater
    )

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