What Are Osmoreceptors?

Osmotic receptors refer to one of the two mechanisms controlling water intake hypothesized in modern doctrines of thirst. Sensitive to chemical concentrations (mainly sodium) in body fluids. Anatomically refers to a part of cells above the pituitary in the hypothalamus. The lack of water can cause dehydration of all cells in the body, but studies have shown that only this part of the cells in the hypothalamus respond specifically to dehydration. Dehydration slightly deforms or shrinks these cells. This physical change causes neural activity, prompts the pituitary gland to release antidiuretic hormones, and sends a signal to the kidneys to reabsorb water from the urine into the blood to dilute the chemical concentrations in the blood and body fluids. Injecting a small amount of saline directly into this area can have an effect similar to long-term dehydration, causing animals to drink a lot of water. ^[1]

Osmotic pressure sensor

Right!

Osmotic receptors refer to one of the two mechanisms controlling water intake hypothesized in modern doctrines of thirst. Sensitive to chemical concentrations (mainly sodium) in body fluids. Anatomically refers to a part of cells above the pituitary in the hypothalamus. The lack of water can cause dehydration of all cells in the body, but studies have shown that only this part of the cells in the hypothalamus respond specifically to dehydration. Dehydration slightly deforms or shrinks these cells. This physical change causes neural activity, prompts the pituitary gland to release antidiuretic hormones, and sends a signal to the kidneys to reabsorb water from the urine into the blood to dilute the chemical concentrations in the blood and body fluids. Injecting a small amount of saline directly into this area can have an effect similar to long-term dehydration, causing animals to drink a lot of water. ^[1]

If the plasma osmotic pressure is increased due to dehydration or injection into the blood vessel with a high concentration of saline and glucose solution, the osmotic baroreceptor will be stimulated to promote ADH secretion, which will cause a sharp decrease in urine output. Conversely, a decrease in plasma osmotic pressure can hinder the secretion of ADH and cause an increase in urine output.

The human osmotic pressure sensor is in the hypothalamus, whose main function is to regulate the body's water balance. When there is too little water in the human body, the osmotic pressure sensor senses that the osmotic pressure in the human body is increased, so it will secrete more antidiuretic hormones, reduce urination, and maintain water. The opposite is true when there is too much water in the human body.

In the regulation of water and salt, the hypothalamic osmotic pressure sensor senses the increase of extracellular fluid osmotic pressure, promotes the release of antidiuretic hormone from the pituitary, promotes the reabsorption of water by the renal tubules and collecting ducts, reduces the urine volume, and condenses the urine. If the extracellular fluid osmotic pressure is reduced, the antidiuretic hormone synthesis and release is reduced, the renal tubules and collecting ducts reduce the water reabsorption, and the urine is diluted, which belongs to negative feedback regulation.