Receptor osmoreceptors

Logically, ADH receptor antagonists, and ADH synthesis and release inhibitors can be effective aquaretics. ADH, 8-arginine vasopressin [113-79-17, is synthesized in the hypothalamus of the brain, and is transported through the supraopticohypophyseal tract to the posterior pituitary where it is stored. Upon sensing an increase of plasma osmolaUty by brain osmoreceptors or a decrease of blood volume or blood pressure detected by the baroreceptors and volume receptors, ADH is released into the blood circulation it activates vasopressin receptors in blood vessels to raise blood pressure, and vasopressin V2 receptors of the nephrons of the kidney to retain water and electrolytes to expand the blood volume. 

Explain how each of the three types of sensory receptors within the digestive tract is stimulated chemoreceptors, osmoreceptors, and mechanoreceptors... 

The osmoreceptors of the hypothalamus monitor the osmolarity of extracellular fluid. These receptors are stimulated primarily by an increase in plasma osmolarity they then provide excitatory inputs to the thirst center and the ADH-secreting cells in the hypothalamus. The stimulation of the thirst center leads to increased fluid intake. The stimulation of the ADH-secreting cells leads to release of ADH from the neurohypophysis and, ultimately, an increase in reabsorption of water from the kidneys and a decrease in urine output. These effects increase the water content of the body and dilute the plasma back toward normal. Plasma osmolarity is the major stimulus for thirst and ADH secretion two additional stimuli include ... 

Liedtke, W., Choe, Y., Marti-Renom, M.A., Bell, A.M., Denis, C.S., Sali, A., Hudspeth, A.J., Friedman, J.M., Heller, S. Vanilloid receptor-related osmotically activated channel (VR-OAC), a candidate vertebrate osmoreceptor, Cell 2000, 103, 525-535. 

Regulation of anti-diuretic hormone secretion is primarily through the plasma osmolarity. Osmolarity is sensed in the hypothalamus by neurons known as osmoreceptors, which in turn stimulate secretion from those neurons that produce anti-diuretic hormone. Secretion of antidiuretic hormone is also simulated by decreases in blood pressure and volume, conditions sensed by stretch receptors in the heart and large arteries. Changes in blood pressure and volume are not nearly as sensitive a stimulator as increased osmolarity, but are nonetheless potent in severe conditions. For example, loss of 15-20% of blood volume by haemorrhage results in a massive secretion of anti-diuretic hormone. Another potent stimulus of anti-diuretic hormone is nausea and vomiting, both of which are controlled by regions in the brain with links to the hypothalamus. 

The stomach empties liquids faster than solids. The rate of transfer of gastric contents to the small intestine is retarded by the activity of receptors sensitive to acid, fat, osmotic pressure and amino acids in the duodenum and the small intestine and stimulated by material that has arrived from the stomach. Gastric emptying is a simple exponential or square-root function of the volume of a test meal - a pattern that holds for meals of variable viscosity. To explain the effect of a large range of substances on emptying, an osmoreceptor has been postulated which, like a red blood cell, shrinks in hypertonic solutions and swells in hypotonic solutions. 

Besides the osmoreceptor mechanism of vasopressin release, the physiological regulation of vasopressin secretion also involves a pressure-volume mechanism that is distinct from the osmotic sensor. AVP release is regulated by baro-receptors that respond to alterations in blood volume. For example, a reduction in plasma volume or arterial pressure,... 

Vasopressin (antidinretic hormone) is a nonapeptide that controls resorption of water by distal tubules of the kidney to regulate the osmotic pressure of blood. It functions to conserve body water by reducing the output of urine, and thus it is known as an antidiuretic. Vasopressin is synthesized in the supraoptic nucleus of the hypothalamus where it is bound to a neurophysin protein carrier, packaged in granules, and delivered by intracellular transport to nerve terminals in the posterior pituitary. Vasopressin bound to neurophysin is released from the granules in response to increased extracellular osmolarity sensed by hypothalamic osmoreceptors, signaling by atrial stretch receptors or after a rise in angiotensin n levels. Its secretion is increased by dehydration or stress and decreased after alcohol consumption. 

Vasopressin is released in response to increased extracellular osmo-larity sensed by hypothalamic osmoreceptors, signaling by atrial stretch receptors or after a rise in angiotensin II levels. Its secretion is increased by dehydration or stress. 

The balance of sodium ion concentrations is governed by a number of mechanisms, including osmoreceptors in the hypothalamus and several volume receptors (e.g., intrathoracic, atrial stretch, and hepatic), and baroreceptors (e.g., intrarenal and arterial). These physiological mechanisms normally balance the plasma sodium and renal excretion of sodium, with approximately 80% of the sodium in the glomerular... 

Although the regulation of the secretion of vasopressin appeared simple a few decades ago and seemed to involve only the activation of the osmoreceptor, it is now clear that a number of factors not related to osmolarity also regulate vasopressin secretion. They include blood volume receptors, systemic barorecep-tors and hormones such as catecholamine, prostaglandins, adrenocortical hormones, thyroid hormones, and the renin-angiotensin system. 

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