Removal of the satiety center causes an animal to eat continuously and he will grow far beyond his normal size. When we are subjected to certain stimuli, the hunger-producing center initiates the eating response. When we have eaten enough, the satiety center tells us to stop. Many of the stimuli that tell the hypothalamus that we are hungry originate in the organs of the body. If the nutrient level of the blood is too low, the hypothalamus is alerted and the feeding center, initiates eating behavior.
External stimuli can also initiate eating behavior.
The sight, sound, and even the thought of food initiate impulses that eventually reach the feeding center in the hypothalamus. Specific hungers are stimulated by specific deficiencies Deficiencies in the body produce a specific hunger for certain foods. Women who are pregnant apparently need a great deal more of certain nutrients than they need normally. There are instances in which women have eaten plaster from walls to provide their bodies with minerals not available to them in any other form. As might be expected, there are specific satiations as well as specific hungers.