all right so in this video we're going to talk about a common question that people have is why does volume contraction lead to a metabolic alkalosis so we're going to make this really simple so let's begin by drawing a nephron over here all right so here we have our nephron of course here we have the proximal convoluted tubule and here we have the distal convoluted tubule and of course filtration goes in this direction over here out into the collecting duct into the toilet so what happens when there's a volume contraction of course that's going to lead to an increase in renin which leads to an increase in aldosterone secretion it's the effect that aldosterone has that leads to the metabolic alkalosis let's explain so what does aldosterone do well the most famous thing that aldosterone does is that it works on the sodium potassium pump and namely it increases its activity so more sodium will be reabsorbed and more potassium will go into the tubule and into the urine so let's focus on this if there's going to be more potassium in the urine there's going to be a hypokalemia so let's take a look at the cell over here so this cell and remember potassium is an intracellular ion so it's primarily inside the cell there's a little bit outside the cell but when there's a hypokalemia that's mainly going to affect the intracellular concentration of potassium and that's going to go down so if potassium goes down inside the cell that will draw hydrogen into the cell because of the charge difference with less hydrogen outside the cell it's going to lead to a metabolic alkalosis okay so that's the first way volume contraction leads to a metabolic alkalosis but aldosterone has another function and that's to work on the hydrogen atpase in the collecting duct and basically hydrogen is dumped into the collecting duct and of course as hydrogen is dumped into the collecting duct there's less hydrogen in the extracellular fluid and that leads again to a metabolic alkalosis so there are two reasons why the increase in aldosterone leads to a metabolic alkalosis and that was caused by this volume contraction okay i hope you enjoyed this scene please subscribe to our channel let me know if you have any questions and take care