1. Antidiuretic hormone (ADH) Good example of Negative feedback loop
ADH – controls reabsorption of water.
ADH increases the permeability of the
distal convoluted tubule and collecting
duct so that more water can be reabsorbed.

2. Therefore a decreased amount of urine results, but an increase in urine concentration. Water and Urea=Urine. Less water, more urea concentration.
Urea is a waste product in the metabolism of proteins. With more water being reabsorbed, blood volume tends to be increased.

3. If too little water is taken in orally the hypothalamus releases a hormone into the nerve tract to the posterior pituitary gland.  

4. The posterior pituitary gland releases ADH and more water is absorbed by the kidneys to maintain blood volume.
pH of blood is maintained by tubular excretion. If pH is too low, hydrogen ions are secreted into the nephron.

6. Alcohol has a negative effect on ADH. It sends a false message to the
hypothalamus that there is too much water in the blood. ADH is not released in fact it is inhibited.

7. Therefore water is not reabsorbed and is lost in the urine
Therefore water is not reabsorbed and is lost in the urine. That is why when you drink alcohol, you urinate a lot and become dehydrated.

8. Aldosterone
Hormones which regulate the level of sodium and potassium in the blood.
If sodium is too low, aldosterone causes more sodium to be reabsorbed. If sodium concentration is high release of aldosterone is inhibited.

9. Inhibits the release of aldosterone

10. Adrenal Cortex controls this hormone
Adrenal Cortex controls this hormone. The effect of this is the same as that of ADH – more water is reabsorbed due to osmosis in the loop of Henle