Portage Learning/BIOD 121 Nutrition module 1Exam Study guide Graded A

Why do we get hungry? Many factors influence what we eat, when we eat and why we eat. However, basic physiological responses play a major role in hunger and satiety. There are two drives that influence our desire to eat. One is hunger and the other is appetite. Although both inform the body that it is time to eat, they are different mechanisms. Hunger is the internal drive to find and eat food and is often experienced as a negative sensation such as churning, growling or a painful sensation in the stomach. Appetite is the external drive that encourages us to find and eat food and since it is related to pleasant sensations associated with food, it can lead us to eat even if we are not hungry. The hypothalamus is a region of the brain that plays a role in hunger as well as satiety and the feeling of being full. When we have not eaten for a period of time, the amount of nutrients in the blood begin to decline. This drop stimulates the feeding center in the hypothalamus which signals us to eat. When the nutrient level of the blood begin to rise, the satiety center is activated and our desire to continue to eat declines. This sounds like a simple process, but in reality the hypothalamus is constantly processing signals from a variety of nerves throughout the body which influence our food intake. If a portion of the hypothalamus is damaged or destroyed, from certain chemicals, trauma, surgery or cancers, the regulation of hunger and satiety can be lost. In such an instance, the body no longer receives signals to stop eating and weight gain is almost certain. There are other factors that determine what we eat and the quantity of food we consume. The gastrointestinal tract (GI) contributes to the feeling of satiety. The GI tract is the main site in the body used for digestion and absorption of nutrients. The GI tract consists of the mouth, esophagus, stomach, small intestine, large intestine rectum and anus. We will be studying the GI tract and its role in nutrition in a later chapter.