Renin-Angiotensin-Aldosterone System

by Thad Wilson, PhD

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    Now, let’s change gears a little bit to talk about the renin-angiotensin-aldosterone system. So the renin-angiotensin-aldosterone system is engaged by decreases in pressure right around the juxtaglomerular apparatus. Again, you have the release of renin, which change angiotensinogen to angiotensin I, and then the ACE, or angiotensin converting enzyme, converts angiotensin I to angiotensin II. We will pause an angiotensin II right now because it is an active or regulated molecule and it's going to be able to enact things or change physiology. So let’s talk through how angiotensin II changes physiology. So angiotensin II causes afferent arteriole constriction and efferent arteriole constriction. Interestingly, the efferent arteriole constriction happens to a greater degree. Therefore, efferent arteriole resistance goes up a little bit more than afferent arteriole resistance. These changes in resistance increase the filtration fraction. By increasing filtration fraction, there’s an increase in the peritubular capillary osmotic pressure. This increase in peritubular capillary osmotic pressure allows for more proximal sodium reabsorption. And of course, if you increase the amount of proximal tubule reabsorption, you’re going to decrease sodium excretion. So that revolves around retaining more sodium. But there’s another effect of this increase in afferent and efferent arteriole resistance, and that is it decreases the peritubular capillary hydrostatic pressure. This also increases proximal tubule reabsorption, and therefore, decreases sodium excretion. So angiotensin II also affects renal blood flow. This decreases the vasa recta blood flow, which decreases the washout of urea, so urea is going to increase. And as urea increases in the interstitial fluid, this changes the gradient for sodium reabsorption, andn this does in the thin ascending limb in the loop of Henle. What ends up happening then is there is an increase in the sodium reabsorption in the loop of Henle, and this also feeds back into...

    About the Lecture

    The lecture Renin-Angiotensin-Aldosterone System by Thad Wilson, PhD is from the course Renal Physiology.

    Included Quiz Questions

    1. Increased hydrostatic pressure
    2. Increased filtration fraction
    3. Increase in plasma sodium level
    4. Increased osmotic pressure
    5. Decreased urea release
    1. Distal convoluted tubules
    2. Collecting duct
    3. Loop of Henle
    4. Proximal convoluted tubule
    5. Bowman's Capsule
    1. ENaC channels are located in apical membrane
    2. Sodium-potassium pump increases sodium ions in tubule cells
    3. ENaC cells channels sodium ions out of tubule cells
    4. ROMK channels are located in basolateral membrane
    5. Aldosterone causes increases sodium ions in tubule lumen

    Author of lecture Renin-Angiotensin-Aldosterone System

     Thad Wilson, PhD

    Thad Wilson, PhD

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