Sodium Regulation by Aldosterone and Angiotensin II – Electrolyte Balance (Nursing)

00:01 There are no known receptors that actually monitor our sodium levels in our bodies fluid.

00:09 Instead, the sodium water balance is linked to our blood pressure and our blood volume control mechanisms.

00:18 Changes in our blood pressure or volume, trigger neural and hormonal controls that will then regulate the sodium content in the different compartments.

00:30 First, let's look at how aldosterone and angiotensin II, two hormones, play a role in our sodium balance.

00:38 Aldosterone plays the biggest role in the regulation of sodium by our kidneys.

00:45 65% of our sodium is reabsorbed in our proximal tubules And about 25 of that is going to be reclaimed in our nephron loops.

00:56 Sodium is never secreted into the filtrate in the kidneys.

01:04 High aldosterone concentrations lead to sodium being actively reabsorbed in the distal convoluted tubules, and the collecting tubules, and water follows closely behind this.

01:19 This will then lead to an increase in the extracellular fluid volume.

01:25 When we have low aldosterone concentrations, salt is not going to be actively reabsorbed, and instead it's going to be lost in our urine.

01:35 Because salt is not coming back into the extracellular fluid compartment, then water is not either.

01:41 So we are also going to lose water in our urine as well.

01:47 We also have the renin angiotensin aldosterone mechanism.

01:53 This actually triggers the release of aldosterone.

01:58 Granular cells of the juxtaglomerular complex are going to secrete renin in response to either sympathetic nervous system stimulation, a decreased filtrate sodium chloride concentration, which is sensed by the macula densa cells of the juxtaglomerular complex or by decreased stretch of our granular cells due to a decrease in our blood pressure.

02:26 The renin is then going to catalyze the production of angiotensin II.

02:33 Angiotensin II then prompts the release of aldosterone from our adrenal cortex.

02:39 And this is going to result in an increase in the amount of sodium reabsorbed by the kidney tubules.

02:48 Aldosterone release can also be triggered by excess levels of potassium in our extracellular fluid.

02:56 Since aldosterone also triggers potassium secretion.

03:02 Aldosterone brings about its effects slowly and this usually takes hours to days to reach some sort of sodium balance.

03:12 So to summarize how our bodies are going to regulate the sodium levels by way of hormones, if we have a decrease in the sodium content in our body, this is going to trigger renin release, which increases the availability of angiotensin II, which will then called the adrenal cortex to release aldosterone, which targets the kidney tubules and causes more reabsorption of sodium.

03:42 This is going to lead to a homeostatic plasma increased level of sodium.

03:49 Also, an increase or excess potassium concentrations and our extracellular fluid compartment also undergo the same cascade of events, but instead of inducing reabsorption, this is going to increase potassium secretion bringing our potassium levels back to homeostasis.