If the osmolarity of blood increases due to sweating, osmoreceptors trigger release of ______ .

Sweating causes a loss of water from the body, which leads to an increase in the osmolarity of blood.

This increase in blood osmolarity is detected by osmoreceptors located in the hypothalamus.

The osmoreceptors stimulate the neurohypophysis (posterior pituitary) to release Antidiuretic Hormone (ADH), also known as vasopressin.

ADH acts on the late distal tubules and collecting ducts of the kidneys to increase water reabsorption, thereby preventing further water loss and helping to restore normal blood osmolarity.

Answer: ADH from neurohypophysis