Hunger - human physiology and animals resulting from lack in the body of nutrients. Externally, the hunger is characterized by behavioral responses aimed at obtaining and eating. Subjectively, people assess the hunger for sensations emanating from a variety of gastrointestinal tract (negative phenomena in the abdomen, related to the motility of the stomach and intestines).
Hunger is based on the excitation of a complex of relevant elements of the Central nervous system, called food centre. The most important among this complex are the front sections of the hypothalamus where there are specific chemoreceptors, reacting on change of a chemical composition of human blood. The reduction of nutrients in the blood ("hungry blood") is captured by these chemoreceptors and results in the stimulation of the cells in the lateral hypothalamus. This excitation is distributed to organs of digestion (the salivary glands, the stomach, the intestines). At the same time the excitement of food center in the hypothalamus gradually covers and other structures of the brain. On this basis, there subjective feelings and begins to form conditioned food-procuring behavior.
By experimental and clinical observations were able to establish that the hypothalamic Department of food center consists of two parts, which were identified as centers of "hunger" and "saturation". If animals in the experiment were destroyed center "hunger", these animals were no longer there, refusing the most delicious food, and died from exhaustion. At destruction of the center "saturation" animals consume large quantities of food, without discrimination especially in its quality. The person similar phenomena are observed in defeat hypothalamic area or pituitary.
The excitability of food center great extent depends on the activities and status of the digestive system. The motility of the gastrointestinal tract, irritation of mucous membranes of the oral cavity with a small amount of nutrients increase the excitement of food center, thereby increasing the overall state of hunger. On the other hand, the deterioration of the digestive tract from poisoning or defeat any disease (ulcer, cancer, dysentery) may inhibit the activity of food center and thus reduce the feeling of hunger until its complete absence (see Anorexia).
Study of physiological mechanisms of the state of hunger, humans allowed in some cases to use it as a therapeutic factor (see Starvation).