2 3 7 Outline The Role Of The Hormones Aldosterone And Adh A

The role of aldosterone and ADH

Hormones are chemical control substances that are secreted by endocrine (ductless) glands, directly into the bloodstream. The travel via the blood, to the target cell – after which the target cell responds. Adjustments to the concentration of water and salts within the urine takes place mainly in the distal parts of the tubules and in the collecting tubules, by altering the permeability of the membranes of cells lining the nephron walls. These changes are brought upon to two hormones, ADH and aldosterone. Aldosterone brings about the retention of salts within the body, and ADH (anti-diuretic hormone) brings about water reabsorption within the body.


A decrease in the concentration of sodium ions in the bloodstream leads to a decrease in blood volume and this stimulates the cells in the cortex of the adrenal gland, which then secretes aldosterone. When aldosterone reaches the kidney, it increases the permeability of the membrane to sodium. Reabsorption of sodium ions from the nephron into the surrounding kidney tissues results and hence salt retention occurs.

Anti-diuretic hormone

When a mammal begins to dehydrate its blood volume drops, this change is detected in the hypothalamus which then stimulates the pituitary gland to secrete ADH. ADH acts on the nephrons in the kidneys to increase the reabsorption of water. The presence of ADH increases the permeability of the membranes in the distal tubules and as a result water is reabsorbed.

Both ADH and aldosterone play an important role in helping the kidney to carry out its homeostatic functions of osmoregulation through the regulation of the solute concentration of the blood (regulated the amount of dissolved ions in the blood) and in regulation of blood volume (maintaining constant fluid volume by producing either large volume of dilute urine, or a small amount of concentrated urine)