Final answer:
Antidiuretic hormone (ADH) is secreted by the hypothalamus and stored in the posterior pituitary gland. It is released in response to increasing osmolarity of tissue fluid, usually due to significant loss of blood volume. ADH signals the kidneys to reabsorb more water, preventing fluid loss in urine and helping to restore blood volume and pressure.
Step-by-step explanation:
Antidiuretic hormone (ADH), also known as vasopressin, is secreted by the cells in the hypothalamus and transported via the hypothalamic-hypophyseal tracts to the posterior pituitary where it is stored until released upon nervous stimulation. The primary trigger prompting the hypothalamus to release ADH is increasing osmolarity of tissue fluid, usually in response to significant loss of blood volume. ADH signals its target cells in the kidneys to reabsorb more water, thus preventing the loss of additional fluid in the urine. This will increase overall fluid levels and help restore blood volume and pressure. In addition, ADH constricts peripheral vessels.