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One of a group of structures in the hypothalamus which respond to changes in osmotic pressure of the blood by regulating the secretion of the neurohypophyseal antidiuretic hormone.



a terminal structure of sensory nerves that reacts to changes, in the concentration of osmotically active substances, that is, to changes in osmotic pressure in the surrounding fluid. Osmoreceptors are found in various animal organs and tissues, such as the liver and pancreas. Impulses from osmoreceptors reach the divisions of the central nervous system that participate in the regulation of water-salt metabolism. Osmoreception is controlled by neurons of the supraoptic nuclei in the hypothalamus. These neurons can perceive fluctuations of as low as 1–2 percent in the osmotic pressure of plasma, and when the osmotic pressure increases, they elaborate the hormone vasopressin, which is stored in the hypophysis. Vasopressin, the antidiuretic hormone, alters the permeability of the walls of the renal tubules when it is released into the blood, thereby reducing the amount of urine excreted.

References in periodicals archive ?
GFR, on the other hand, is influenced by volume sensors, osmoreceptors, and arterial oncotic pressure.
Osmoreceptors in the hypothalamus are sensitive to overall fluid balance and release ADH accordingly.
24~ showed an inadequate rise in urine osmolality after 54 h of water deprivation in elderly subjects, and suggested that there was a dysfunction of the osmoreceptor leading to inadequate AVP release.
Rather, it seems more likely to be localized in the pathways from the osmoreceptor neurons to the cortex.
Osmoreceptors in the hypothalamus and heart/blood vessel baroreceptors detect changes in plasma concentrations, producing or reducing anti-diuretic hormone (ADH) concentrations to increase, or decrease water absorption respectively (von Duvillard, 2004).
It appears as though the osmoreceptors are 'reset' at a lower level to avoid a continuous diuresis.
Another interesting observation is the localization of AQP4 in the neurohypophysis, where osmoreceptors control the release of ADH by an undefined process.
When body water is lost, osmoreceptors in the hypothalamus sense an increased body fluid osmolarity and stimulate the secretion of AVP.
Osmoreceptors in the hypothalamus itself cause the pituitary to increase ADH levels when plasma osmolality increases as little as 1-2% [2,7] Baroreceptors, especially in the heart and the carotid sinus, [10] monitor changes in blood volume and pressure and indirectly signal the hypothalamus to regulate ADH according to perceived changes.