Osmoregulation

the process of actively maintaining the osmotic pressure of bodily fluids like water and dissolved substances

Aldosterone

What is it?

• It is a steroid hormone produced in the outer section of the adrenal glands which are located above the kidneys.
• It is part of a group of linked hormones, which form the renin–angiotensin–aldosterone system.
• The beginning of the system starts with renin which is an enzyme that leads to a series of chemical reactions resulting in the production of angiotensin 2, which therefore stimulates aldosterone release.
• It regulates salt and water levels in the body, therefore having an effect on blood pressure.

What does it do?

• If blood pressure drops below typical levels or there is a decrease in blood flow to the kidneys causing a loss of blood volume, aldosterone is released.
• It then travels through cell membranes and attaches to certain receptors which are only found in certain cells, like cells in the kidneys, sweat glands, and colon.
• These receptors then act as a transcription factor for a certain gene, which ends up resulting in the synthesis of proteins that increase sodium reabsorption and the amount of potassium removed in the urine.
• When the sodium in the blood increases, the increase in water retention follows and thus blood pressure.
• Therefore aldosterone indirectly balances blood levels of electrolytes (including sodium, potassium and hydrogen) and aids to keep the blood pH consistent.
• When salt levels and blood pressure return back to normal and the body is once again hydrated, the amount of renin in the bloodstream falls and therefore the amount of aldosterone also decreases. This results in more water excretion through the urine.
• Also known as a negative feedback system.