Mineralocorticoids (Nursing)

00:00 The mineralocorticoids that are produced by the adrenal cortex are going to be responsible for the regulation of our electrolyte concentrations such as our sodium and potassium concentrations found in our extracellular fluids. The importance of sodium is that it's going to affect our extracellular fluid volume as well as our blood volume, blood pressure, and the levels of other ions in our body. Potassium is going to be important as it's responsible for setting the resting membrane potential of cells. Aldosterone is the most potent of our mineralocorticoids. It's responsible for stimulating sodium reabsorption by the kidneys. Sodium reabsorption results in an increase in our blood volume and our blood pressure as the fluids in the kidneys are going to follow these sodium molecules out of the kidneys and into the blood.

01:03 Aldosterone is also important for the stimulation of potassium elimination by the kidneys in order to maintain potassium homeostasis. The effects of aldosterone are short-lived. It's going to stimulate the synthesis and the activation of an ATPase known as the sodium-potassium pump. This is where sodium and potassium are going to be exchanged inside and out of the cell in active transport. There are several different factors that are going to regulate our aldosterone secretion. First, we have the renin-angiotension-aldosterone mechanism. Second, plasma concentrations of potassium. Third, we have our ACTH. And finally, we have the atrial natriuretic peptide. So starting with the renin-angiotension-aldosterone mechanism, this is going to be responsible for stimulating the special cells in the kidneys in response to a decrease in the blood pressure. These cells are then going to release renin into the blood.

02:22 The renin will then cleave off parts of the plasma protein, angiotensinogen, and this is going to trigger this enzyme to cascade until we get to angiotensin II. Angiotensin II is then a potent stimulator of aldosterone release. Other factors that are going to affect aldosterone release include the plasma concentrations of potassium. Increased potassium in the blood is going to directly influence the zona glomerulosa cells of the adrenal cortex to release aldosterone. This causes a secretion and subsequent excretion of potassium. Low levels of potassium inhibit aldosterone release. The adrenocorticotropic hormone or ACTH is also going to affect aldosterone release. It can cause a small increase of aldosterone during periods of increased stress. And lastly, atrial natriuretic peptide or AMP is secreted by the heart in response to high blood pressure. It then blocks renin and aldosterone secretion in order to have the reverse effect to decrease blood pressure. Since renin and aldosterone lead to an increase in blood volume, which would lead to an increase in blood pressure, this is going to be responsible for counteracting the effect of aldosterone and renin.