What is the function of osmoreceptors ?

Osmoreceptors in the body are activated by changes in blood volume, body fluid volume and ionic concentration. 

These are present in hypothalamus. These send impulses to posterior lobe of pituitary gland to secrete ADH. The ADH (Anti diuretic hormone) increases the permeability of cells of distal convoluted part and collecting tube to absorb more water and produce hypertonic urine.