Final answer:
Antidiuretic hormone (ADH), or vasopressin, is a peptide hormone produced by the hypothalamus and released from the posterior pituitary gland. It conserves water by acting on the kidneys to increase water reabsorption and regulates blood pressure through vasoconstriction.
Step-by-step explanation:
The antidiuretic hormone (ADH), also known as vasopressin, belongs to a group of hormones known as peptide hormones. This particular hormone is synthesized by cells in the hypothalamus and released from the posterior pituitary gland.
The primary function of ADH is to regulate the body's retention of water by acting on the kidneys, specifically on the collecting ducts where it promotes water reabsorption into the bloodstream.
When the osmoreceptors in the hypothalamus detect an increase in blood plasma concentration, indicating dehydration or loss of blood volume, ADH is released.
It works by inserting aquaporins into the membranes of kidney tubules, which allows water to reenter the capillaries by osmosis, thereby concentrating the urine and reducing water excretion.
Moreover, ADH serves as a vasoconstrictor to increase blood pressure, which is particularly critical during hemorrhaging.
Thus, the principal action of ADH is crucial in maintaining homeostasis regarding fluid balance and blood pressure in the human body.