Give an example of a negative feedback mechanism in the human body.

When the hypothalamus in the brain detects that the blood is getting too concentrated (not enough water), it stimulates the pituitary gland to release an anti-diuretic hormone (ADH). When it reaches the kidneys it causes them to reabsorb more water, which results in more concentrated urine. This hopefully restores the blood water level back to normal (though it would obviously fail if no water was taken in by the human for a long time). An inverse process occurs when the blood is too dilute (though I'll not elaborate on it here for sake of space).