osmoreceptors

Examples of osmoreceptors in the following topics:

• Regulation of Water Intake

  • An osmoreceptor is a sensory receptor, primarily found in the hypothalamus of most homeothermic organisms, that detects changes in osmotic pressure.
  • Osmoreceptors detect changes in plasma osmolarity (ie. concentration of solutes dissolved in the blood).
  • When the osmolarity of blood changes (i.e. it is more or less dilute), water diffusion into and out of the osmoreceptor cells changes.
  • When the osmoreceptors detect high plasma osmolarity (often reperesenting a low blood volume), they send signals to the hypothalamus, which creates the biological sensation of thirst, and also stimulates vasopressin (ADH) secretion, which starts the events that will reduce plasma osmolarity to normal levels.
  • The macula densa cells in the walls of the ascending loop of henle of the nephron is another type of osmoreceptor, however it stimulates the juxtaglomerular apparatus (JGA) instead of the hypothalamus.

• Regulation of Urine Concentration and Volume

  • The increased plasma osmolarity is sensed by osmoreceptors in hypothalamus, which will stimulate the posterior pituitary gland to release ADH.
  • After ADH acts on the nephron to decrease plasma osmolarity (and leading to increased blood volume) and increase urine osmolarity, the osmoreceptors in the hypothalamus will inactivate, and ADH secretion will end.

• Classification of Receptors by Stimulus

  • For example, hygroreceptors that respond to changes in humidity and osmoreceptors that respond to the osmolarity of fluids may do so via a mechanosensory mechanism or may detect a chemical characteristic of the environment.

• Regulation of Water Output

  • Osmoreceptors in the hypothalamus detect the increased plasma osmolarity and stimulate the posterior pituitary gland to secrete ADH, which is also known as vasopressin.

• Production of Dilute and Concentrated Urine

  • To explain more scientifically, as the body becomes fluid-deficient, this is sensed by osmoreceptors in the organum vasculosum of lamina terminalis and subfornical organ.

• Overview of the Urinary System

  • A basic example is that a decrease in water concentration of blood is detected by osmoreceptors in hypothalamus, which stimulates ADH release from pituitary gland to increase the permeability of the wall of the collecting ducts and tubules in the nephrons.