The effect of ADH on tubule permeability and water balance 鈥 Higher
ADH
Two important areas inside the brain are the The part of the brain that detects changes in blood temperature and water concentration., which detects changes in the blood plasma, and the An endocrine gland that is located just below the centre of the brain. It releases a number of important hormones., which regulates the release of the anti-diuretic hormone, known as A hormone produced in the pituitary gland that controls the volume and concentration of urine..
Different amounts of ADH are released into the bloodstream according to the concentration of water in the The liquid part of the blood containing useful things like glucose, amino acids, minerals, vitamins (nutrients) and hormones, as well as waste materials such as urea.. ADH is released by the pituitary gland when the blood is too concentrated and it causes the kidney tubules to become more A substance which allows fluids or gases to pass through it.. This allows more water to be reabsorbed back into the blood during selective reabsorption.
The diagrams show what happens when there is either too little or too much water in the blood.
If a person has consumed a large volume of water and has not lost much as sweat, too much water might be detected in the blood plasma. If this occurs, less ADH will be released, which results in less water being reabsorbed and a dilute and larger volume of urine will be produced.
If a person becomes too hot and sweats a lot, but doesn't drink enough water to replace what was lost, too little water might be detected in the blood plasma. More ADH will be released, which results in water being reabsorbed and a more concentrated but smaller volume of urine will be produced.
| Plasma | Problem | ADH release | Effect of ADH | Effect on urine |
| High concentration | Too little water | Increases | More water reabsorbed by nephrons | More concentrated |
| Low concentration | Too much water | Decreases | Less water reabsorbed by nephrons | More dilute |
| Plasma | High concentration |
|---|---|
| Problem | Too little water |
| ADH release | Increases |
| Effect of ADH | More water reabsorbed by nephrons |
| Effect on urine | More concentrated |
| Plasma | Low concentration |
|---|---|
| Problem | Too much water |
| ADH release | Decreases |
| Effect of ADH | Less water reabsorbed by nephrons |
| Effect on urine | More dilute |
This type of control is an example of the negative feedback mechanism. It aims to keep the concentration of the blood plasma constant.
A negative feedback control system responds when conditions change from the ideal or set point and returns conditions to this set point. There is a continuous cycle of events in negative feedback.