11.01 Renin Angiotensin Aldosterone System

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  1. Renin Angiotensin Aldosterone System helps the body…
    1. Regulate blood pressure
    2. Regulate blood volume
    3. Regulate fluid and electrolytes
  2. RAAS is actived when the kidneys sense…
    1. Hypotension
    2. Decreased blood volume (blood loss, severe dehydration)
    3. Lack of blood flow to the kidneys.
  3. Understanding RAAS helps better understand the following medication classes
    1. Angiotensin Converting Enzyme Inhibitors
    2. Angiotensin II Receptor Blockers (ARBS)
    3. Renin Antagonists

Nursing Points


  1. Goals of RAAS-
    1. Improve perfusion to the kidneys
    2. Increase blood pressure
    3. Increase blood volume
  2. How the RAAS works-
    1. Kidneys sense they are getting a decreased amount of blood flow
    2. Kidneys activate the RAAS by releasing the hormone renin
    3. Renin converts Angiotensinogen (an inactive protein) to Angiotensin I (active)
    4. Angiotensin I goes to the lungs where it is converted to Angiotensin II
      1. Converted by an enzyme called an angiotensin-converting enzyme (also known as ACE – a la ACE Inhibitor)
    5. Angiotensin II has a lot of functions in the body
      1. Increases sympathetic nervous system response causing vasoconstriction
        1. This increases blood pressure
      2. Causes kidneys to reabsorp more sodium which increases water retention
        1. This increases blood volume
      3. Causes the pituitary gland to increases secretion of Anti-diuretic Hormone (ADH)
        1. This increases water reabsorption in the kidneys
      4. Causes the adrenal gland to increase secretion of Aldosterone (another hormone)
        1. Causes the kidneys to increase their sodium and water retention
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Okay, so we gonna talk about the RAA System in our body and the reason that we gonna talk about RAA system and covering it in our video, that it will help to better understand the Angiotensin Converting Enzyme Inhibitor medications, ARBs which is also called as Angiotensin II receptor blockers and Renin Antagonists. So, if you have a better understanding of the RAA system in our body, it will really help you to understand these 3 pharmacological classes of drugs and it will helpful to understand the side effects, why do we have the side effects and why do we use this medication for the particular diseases.

So, let’s go to the next slide and have a take a look at the RAA system. So, this diagram is basically presenting the RAA system. It may look complicated at first look, but it’s not really. So, if you look at the renin enzyme right here, we have a renin enzyme that gets secreted by the kidneys. When our kidney does not get enough blood flow or due to the blood pressure fall or if we have a blood loss, or it could be different reasons that the kidney is not getting enough blood flow. Or, if our body does not have enough sodium to reabsorb the water, kidney is not getting enough blood flow. Then, there’s a specialized cell in the kidney that’s gonna release renin. Now, what this renin gonna do, it’s gonna convert angiotensinogen protein which is in the inactive form in our blood to angiotensin I. So, the work of the renin, it’s gonna convert angiotensinogen to the angiotenisin I. Now, when the angiotensin I goes to the lungs, through the blood stream, the enzyme here, it’s called ACE inhibitor, right here in the lungs, gonna convert this angiotensin I into angiotensin II. So, this is the enzyme which is really important to remember. This is gonna help you in the ACE inhibitors. So, this is called Angiotensin Converting Enzyme which is present in the lung. Now, when angiotensin I gets converted into the angiotensin II, angiotensin II has many effects on our body. The first effect, when you take a look, it’s gonna increase the sympathetic system. Okay, so when it does increase the sympathetic system, nervous system, it’s gonna increase the vasoconstriction and if you really know your sympathetic nervous system. It’s gonna cause the vasoconstriction and it’s gonna increase the blood pressure. When there’s an increase in the blood pressure, kidneys gonna get enough blood flow. That’s how kidneys gonna get re-perfused. Now, the second action that angiotensin II have is on the kidney tubules. Well, it’s gonna increase the reabsorption of sodium and it’s gonna increase the excretion of potassium. Now, when it increases the reabsorption of sodium, it’s gonna increase the H2O retention, basically, the water retention. When that happens, it’s gonna increase a lot of volume, blood volume increases. When the blood volume increases, it’s gonna increase the blood pressure and that’s how it’s gonna cause, that’s how the kidneys get re-perfused which is the main problem why the renin got secreted. It also has effect on the adrenal gland as well. Angiotensin II is gonna go to the adrenal gland and it’s gonna increases the secretion of Aldosterone which is basically gonna do the same thing. Increase the sodium reabsorption, and it’s gonna increase the potassium excretion. Sodium reabsorption is gonna increase the water reabsorption as well as it’s gonna increase the blood volume. And, the final effect that angiotensin II has, it’s on the collecting ducts of the kidney. Our collecting ducts gonna, it’s main site where all the water excretion or the reabsorption happens. So, what it’s gonna do is it’s gonna go to the pituitary gland and gonna increase the secretion of ADH which is also called as antidiuretic hormone. What this antiduretic is gonna do, it’s gonna increase the water reabsorption in the kidney and it’s gonna increase blood volume. And that’s how kidney is gonna get re-perfused. So, this is how basically the RAA System works, so, have a better understanding of the RAA System and then we can understand ACE inhibitors, ARBs inhibitors and renin antagoist medication wear easily, which we’re gonna cover in the following presentation.

If you have any question about RAA System, then you can e-mail us or contact us. Thanks.

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