What is the role of ADH in water balance?

ADH, or antidiuretic hormone, helps to regulate the body's water balance by controlling the amount of water reabsorbed by the kidneys.

ADH, also known as vasopressin, is a hormone produced in the hypothalamus and stored in the pituitary gland at the base of the brain. It plays a crucial role in maintaining the body's water balance. When the body is dehydrated, the concentration of solutes in the blood increases. This is detected by osmoreceptors in the hypothalamus, which then stimulate the release of ADH.

Once released, ADH travels in the bloodstream to the kidneys. Here, it acts on the cells of the collecting ducts, making them more permeable to water. This means that more water is reabsorbed back into the bloodstream, rather than being excreted as urine. As a result, the urine becomes more concentrated and the volume of urine produced decreases. This helps to conserve water and restore the body's water balance.

On the other hand, when the body is well hydrated, less ADH is released. This makes the collecting ducts in the kidneys less permeable to water, so less water is reabsorbed and more is excreted as urine. This helps to prevent water overload and maintain the right balance of water in the body.

In addition to its role in water balance, ADH also has a vasoconstrictor effect. This means it can narrow the blood vessels, which increases blood pressure. This is another way in which the body can respond to dehydration, as increased blood pressure helps to push water back into the cells from the bloodstream.

In summary, ADH is a vital hormone for maintaining the body's water balance. It does this by controlling the amount of water reabsorbed by the kidneys, and by adjusting blood pressure in response to changes in hydration levels.