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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.