Osmoregulation is the active regulation of the
osmotic pressure of an
organism's
body fluids, detected by
osmoreceptors, to maintain the
homeostasis of the organism's
water content; that is, it maintains the
fluid balance and the
concentration of
electrolytes (
salts in
solution) to keep the fluids from becoming too diluted or concentrated. Osmotic pressure is a measure of the tendency of water to move into one
solution from another by
osmosis. The higher the osmotic pressure of a solution, the more water tends to move into it. Pressure must be exerted on the
hypertonic side of a selectively permeable
membrane to prevent
diffusion of water by osmosis from the side containing pure water.
Osmoregulation, in
biology, maintenance by an organism of an internal balance between
water and dissolved materials regardless of environmental conditions. In many marine organisms
osmosis (the passage of solvent through a semipermeable membrane) occurs without any need for regulatory mechanisms because the cells have the same osmotic pressure as the sea. Other organisms, however, must actively take on, conserve, or excrete water or salts in order to maintain their internal water-mineral content.