Osmoreceptor

Osmoreceptors are specialized cells, which measure the osmolarity of the liquid outside the cell. They sit in the hypothalamus and in the juxtaglomerular apparatus of the kidney.

Operation

The inner cell cytoplasm has a well-defined osmolarity of 290 mosmol.

When the extracellular osmolarity equal to the intracellular, so the diffusion flows offset into the cell and out of the cell from, in total there will be no liquid flow.

However, if the osmolarity of the cell from outside - for example, by increased salt loss, as the liquid flows along the osmotic gradient from the outside into the cell. The following is a cell swelling. Due to this swelling open mechanosensitive ion channels. The result is a depolarization of the cell membrane and thus the release of transmitter substances or the generation of an action potential. Accordingly, the cells hyperpolarize when increasing the osmolarity beyond the cell. This also conveys the feeling of thirst.

Unclear so far is the question of the termination of sense of thirst while drinking. Until the amount of liquid taken namely the blood and osmoreceptors has reached the brain, it takes a few minutes. The feeling of thirst, however, already disappears while drinking after seconds.

The body has a number of hormones involved in homeostasis of the osmolarity. These measures are mainly the vasopressin or antidiuretic hormone ( ADH), aldosterone and atrial natriuretic peptide (ANP or ANF).

• Cell type
• Osmosis