Negative feedback and osmoregulation

In the body of an animal conditions such as water concentration, temperature, and glucose concentration must be kept as constant as possible. Control systems that keep such conditions constant are examples of homeostasis; this is the maintenance of constant internal conditions in an organism.

Negative feedback is an important type of control that is found in homeostasis.

Stages in negative feedback

An example of negative feedback can be seen in osmoregulation; the control of water concentration in blood and body fluids.

Here are the important facts about osmoregulation:

• The pituitary gland controls blood water concentration.
• This gland produces the hormone ADH.
• ADH is carried by the blood to the kidneys.
• ADH increases the permeability of the kidney tubules allowing water to be reabsorbed from the tubules into the blood.
• If blood water concentration falls, more water reabsorption is needed so that less water is lost as urine. ADH production is increased.
• If blood water concentration rises, less water reabsorption is needed so that more water is lost as urine. ADH production is decreased.

This information can be arranged into a cycle which is an example of negative feedback:

The cycle of negative feedback