Osmoreceptors play a role in the regulation of "sodium and water balance" that maintains the osmotic pressure within the body (Bourque & Oliet 1997). If this balance is offset, the osmoreceptors are able to alert the body to change the behavior to return to a state of homeostasis.
Mechanism
The osmolality of the animal is crucial to maintain a consistent blood osmotic pressure, failure to do so will upset the balance of the body chemistry and can lead to various problems (Hill et al. 2016). Osmoreceptors are defined as "groups of specialized nerve cells capable of transducing changes in external osmotic pressure into meaningful electrical signals" (Bourque et al. 1994). The presence of these receptors near where food and fluids are taken in is to help with an "early detection". To maintain osmotic regulation, the afferent neurons "that innervate hepatic blood vessels" are able to "detect physiological hyposmotic shifts in blood osmolality" (Lechner et al. 2011). With the presence of slight shifts in to hypo osmotic levels, the hepatic sensory neurons activate an ionic current that are similar to a receptor channel protein. These sensory afferents that detect changes are capable of signaling for shifts to occur, such as making the host, the human in this case, drink more water.