Sodium balance is regulated primarily by control of amount(s) a. ingested, b. excreted in urine, c. lost in perspiration, d. lost in feces.

Video transcript

Hi, everyone. And welcome back. Our next question says when sodium intake is high, the kidneys increase sodium excretion to maintain balance. Conversely, when sodium intake is low, the kidneys reduce sodium excretion to conserve sodium and prevent a deficit. Which of the following hormones directly affects the excretion of sodium in urine. A Aldo B cortisol C antidiuretic hormone or A DH or D atrial nature erratic peptide or A NP. Well, this one's a bit tricky because all of these hormones have a role in maintaining fluid balance and do affect sodium concentrations. But our key here is which hormone directly affects the excretion of sodium in urine. So it's direct action affects how much sodium is excreted. And with that, as our guide, our answer will be choice. A aldosterone. When aldosterone is released, it causes increased reabsorption of sodium ions from the kidneys or buy the kidneys, I should say and that's balanced because you can't just uh grab on to more positively charged ions without balancing the charge somehow that's balanced by increased excretion of potassium ions. So, as we can see, this is a direct effect on the excretion of sodium in the urine it decreases the amount that will be excreted. So that's why choice A is correct. Let's look at our other answer. Choices. When we look at cortisol, cortisol like aldosterone is released by the adrenal gland and it does have an effect on sodium balance and it has an effect on sodium levels because it influences the fluid balance uh due to its effect on blood pressure and its effect on other hormones that affect it. Cortisol means stress hormone, it gets released when the body is under stress, but it doesn't have a direct effect on sodium levels. So it's not our answer choice. C anti diuretic hormone causes increased water reabsorption by the kidneys by increasing the amount of aquaporin in the me cell membranes. Those are water transport proteins. So more water gets reabsorbed and just by osmotic pressure, more sodium follows the water. So if you keep that in mind, sodium ions tend to follow water in the kidney systems. So the increased water reabsorption leads to increased sodium reabsorption, but it's not a direct effect. Its direct effect is on the aquaporin which increase the water reabsorption. So that's why it's not correct. And finally, our A NP is when the blood volume increases, it's released by the cells in the atria. Um in response to higher atrial pressure. And the result of that, when you have increased blood volume, it promotes water and sodium excretion from the kidneys to lower the blood volume. So it has kind of the opposite effect of A DH. And this one's a little bit trickier because it is a more connected effect on the excretion of sodium. But its main purpose is to regulate blood volume, not to maintain sodium levels. So it responds mainly just to that blood volume signal regardless of what the sodium level is in the blood. So that's why choice A is a better answer than choice. D So again, which of these hormones directly affects the excretion of sodium in urine. Choice A aldosterone which causes an increased reabsorption of sodium by the kidneys. See you in the next video.