Potassium – Electrolyte Balance (Nursing)

00:01 So now let's look at another electrolyte.

00:05 Potassium.

00:07 Potassium affects the resting membrane potentials in our neurons and our muscle cells, especially our cardiac muscle cells.

00:16 An increase in the extracellular fluid osmolality of potassium would cause a decrease in our resting membrane potential, which would cause a depolarization of the membrane, which will lead to a reduced excitability of the cells.

00:34 That's a bad thing.

00:36 Also, if there is too little potassium, in our extracellular fluid, this could cause a hyperpolarization of our membrane potentials, which could lead to non-responsiveness of our cardiac muscle cells.

00:52 Therefore, a disruption in our potassium concentrations, either hyper or hypo kalemia in the heart can interfere with the electrical conduction and can also lead to sudden death.

01:08 Because of this, our homeostasis of our potassium levels is vital for us to survive.

01:17 So, our potassium balance is going to be controlled in the cortical collecting ducts of the kidneys by regulating the amount that is going to be secreted into our filtrate.

01:31 If there is a high potassium content in our extracellular fluids, this is going to favor the principal cells of the collecting tubes to secrete more potassium.

01:44 If, however, we have low potassium levels, this would cause those principal cells to reduce the secretion of potassium to a minimum so that we hold on to as much potassium as possible.

01:59 Also, type A intercalated cells are able to reabsorb some of the potassium that is left in our filtrate.

02:08 Our kidneys have a very limited ability to retain potassium.

02:13 So most of the potassium that makes it to the kidneys is going to be lost in urine.

02:19 And this can sometimes lead to a deficiency, if we do not replace our potassium in our diet.

02:27 This is why it's important to eat bananas.

02:31 So the most important factor that's going to affect potassium secretion is going to be its concentration in our extracellular fluids.

02:42 A diet that is high in potassium would lead to an increase in the amount of potassium found in our extracellular fluid.

02:52 Again, potassium entry into the principal cells of the collecting tubule of the nephron would lead to an increase in the amount of potassium secreted, and then released into our urine.

03:06 If however, we have a low potassium diet, or if we are under a situation where we have an accelerated potassium loss, this would reduce its secretion, and promote its very limited reabsorption.