Vasopressin is released once the
osmoreceptors in the hypothalamus detect an increase in serum osmolality or the baroreceptors detect hypovolaemia.
The MnPO receives inputs from the circumventricular organs and peripheral
osmoreceptors with reciprocal connections with paraventricular nucleus of hypothalamus (PVN), parabrachial nucleus, and ventrolateral medulla that are involved in cardiovascular regulations [14, 27-31].
However, simultaneously with the activation of facilitatory mechanisms, increased activity of
osmoreceptors produced by hyperosmolarity also activates LPBNinhibitory mechanisms, which strongly curb sodium appetite (43,45) (Figure 1).
If you get too little liquid, it's going to shrink your cells, and
osmoreceptors in your brain and other parts of your body are going to sense that cells need water.
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.
GFR, on the other hand, is influenced by volume sensors,
osmoreceptors, and arterial oncotic pressure.
Two afferent pathways, one from baroreceptors and one from
osmoreceptors, control the secretion of AVP in the presence of hypovolemia or hyperosmolality.
Dry mucous membranes, hyperosmolality, and reduced plasma volume activate hypothalamic
osmoreceptors, which trigger thirst and stimulate the secretion of ADH from the posterior pituitary.