Afferent and Efferent Arterioles

by Thad Wilson, PhD

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    00:01 So if we think then about what changes the amount of filtration, we have a couple of different variables to talk about.

    00:09 One is whether the afferent arteriole could change in size? So if you get a vasoconstriction or a decrease in the luminal diameter of the afferent arteriole, it means that you are going to have less pressure within the glomerular capillary.

    00:27 So what does that look like in terms of a picture? If you decrease the fluid traveling past the afferent arteriole, what’s going to happen is you’ll have a decrease in the pressure of the capillaries in Bowman’s space.

    00:44 So you get a decrease in [P sub GC].

    00:49 That decrease is [P sub UF], and what that is the pressure of the ultrafiltrate.

    00:55 It also means you get a decrease in the glomerular filtration rate.

    01:00 You get a decrease in the amount of flow through the renal tubule, and finally you get a decrease in the amount of renal blood flow.

    01:10 So afferent arteriole vasoconstriction can be summarized by decreasing all of our parameters – the plasma and the pressure of the ultrafiltrate, glomerular filtration rate, renal tubule flow, and renal blood flow.

    01:26 Now what happens if the opposite occurs - if we dilate the afferent arteriole? So, again, dilation is simply making that tubule bigger, and therefore more flow can go through it.

    01:38 If more flow goes through the afferent arteriole, that’s going to increase the pressure of the ultrafiltrate, that’s going to increase the pressure within Bowman’s capillary.

    01:52 It also increases glomerular filtration rate, and increases renal tubule blood flow.

    01:59 So afferent arteriole vasodilation increases all four parameters.

    02:06 Now let’s talk about the efferent arteriole.

    02:09 This one gives people a little bit more of a headache, so let’s go through it a little bit slower.

    02:14 Afferent arteriole constriction decrease all of our variables.

    02:19 Afferent arteriole vasodilation increase all of our variables.

    02:24 So what happens if you constrict the efferent arteriole? So you’re decreasing flow after the fact after it travels through the glomerular capillary.

    02:37 What does that do? Well, it causes there to be an increase in the pressure of the glomerular capillaries.

    02:46 Because if you decrease or cause a constriction, you decrease the flow that goes through.

    02:55 But in front of that constriction, what happens is pressure builds up.

    03:01 It’s kind of like damming up a river.

    03:03 You’re going to get an increase in the fluid in front of the constriction that increases the pressure within the glomerular capillary, increases glomerular filtration rate.

    03:16 And what that does then is increase renal tubule flow.

    03:22 The downside is, it does decrease renal blood flow – an efferent arteriole vasodilation.

    03:31 So now, what this does is, it opens up the outlet vessel a little bit larger.

    03:39 What this does is decrease the amount of pressure of ultrafiltrate.

    03:46 It decreases the glomerular filtration rate.

    03:49 It decreases renal tubule flow, but it increases renal blood flow.

    03:56 Efferent arteriole changes – if we have to think about it – what would happen if you change the size of the blood vessels as the blood is leaving the glomerular capillary? Will it have any build-up effects? And then on the afferent arteriole side, it’s simply – are you increasing or decreasing the diameter of what’s entering the glomerular capillaries?

    About the Lecture

    The lecture Afferent and Efferent Arterioles by Thad Wilson, PhD is from the course Renal Physiology.

    Included Quiz Questions

    1. Efferent arteriole constriction
    2. Efferent arteriole dilation
    3. Afferent arteriole constriction
    4. Afferent arteriole dilation
    1. Increased pressure of the ultrafiltrate
    2. Decreased pressure within Bowman’s capillary
    3. Decreased glomerular filtration rate
    4. Increased pressure within Bowman’s capillary but a decreased GFR
    5. Decreased pressure of the ultrafiltrate

    Author of lecture Afferent and Efferent Arterioles

     Thad Wilson, PhD

    Thad Wilson, PhD

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    Incredibly clear
    By Lilas H. on 02. December 2016 for Afferent and Efferent Arterioles

    Incredibly clear, natural lecture style. Excellent companion to my textbook.