38.1 – Describe the physiological factors that produce hunger. The Physiology of Hunger The most important signals that start and stop hunger come from the blood. The brain monitors both the amount of nutrients absorbed in the blood sent from the digestive system and the level of hormones released into the blood in response to the nutrients in the bloodstream.  As food moves from the stomach to the bloodstream, a hormone called CCK (cholecystokinin) is released; this hormone is detected by the brain, where it acts as a neurotransmitter signifying short-term satiation. In other words, CCK is responsible for indicating fullness during a meal.  Leptin is another hormone that indicates satiation. Leptin is released into the bloodstream as the fat supplies increase; it then notifies the brain to stop eating. When leptin levels are high, causes the brain to increase metabolism and decrease hunger; when leptin levels are low, feelings of hunger increase. Ghrelin is a hormone secreted by an empty stomach; sends “I’m hungry” signals to the brain. PYY is a digestive tract hormone which sends “I’m not hungry” signals to the brain. The brain also monitors glucose levels to determine hunger or satiation. Glucose is sugar that the body uses for energy. When glucose levels drop, the individual experiences hunger. Insulin has an effect on the amount of glucose in the body. Insulin is a hormone that is used to concert glucose to energy. When insulin levels rise, glucose levels decrease, causing the sensation of hunger.

38.1 – Describe the physiological factors that produce hunger.

38.1 – Describe the physiological factors that produce hunger.

38.1 – Describe the physiological factors that produce hunger. Hormone Tissue/Location Response Orexin increase Hypothalamus Increases hunger Ghrelin increase Stomach Insulin increase Pancreas Leptin increase Fat Cells Decreases hunger PYY increase Digestive tract

38.1 – Describe the physiological factors that produce hunger. The Brain’s Role in Hunger The hypothalamus was the first area of the brain to be seen as the control center for hunger. The ventromedial hypothalamus stops hunger. Destroy the ventromedial hypothalamus and the animal eats excessively. The lateral hypothalamus initiates hunger. Destroy the lateral hypothalamus and the animal has no interest in eating. If the lateral hypothalamus is stimulated, orexin is released (hunger-triggered hormone). Set Point: the point at which an individual’s “weight thermostat” is supposedly set. When the body falls below this weight, an increase in hunger and a lowered metabolic rate may act to restore the lost weight. Basal Metabolic Rate: regulates the expenditure of energy used to maintain our body’s vital functions.

38.2 – Discuss cultural and situational factors that influence hunger. The Psychology of Hunger Memory plays an important role in hunger. Due to difficulties with retention, amnesia patients eat frequently if given. This suggests that part of knowing when to eat is our memory of our last meal. Taste Preference: Biology and Culture Body chemistry and environmental factors influence not only when we feel hunger, but what we feel hungry for (Taste Preferences). Situational Influences on Eating We eat more when eating with others. When given a large serving utensils or a large bowl/plate, we take more food. When offered a supersized portion, we put away more calories (Unit Bias)

38.3 – Discuss the factors that predispose some people to become and remain obese. Obesity: is a disorder characterized by being excessively overweight. Obesity increases the risk for health issues like cardiovascular diseases, diabetes, hypertension, arthritis, and back problems.   The Genetic Factor  Studies reveal that body weight has a genetic basis. Identical twins have closely similar weights, even when reared apart. Given an obese parent, boys are 3 times more likely, and girls 6 times more likely to be obese that those with normal-weight parents. Adoptive siblings’ body weights are uncorrelated; people’s weights resemble those of their biological parents and siblings. Activity Levels Lack of exercise is a major contributor to obesity. Just watching TV for 2 hours resulted in a 23% increase of weight when other factors were controlled. Food Consumption  Over the past 40 years, average weight gain has increased. Health professionals are pleading with US citizens to limit their food intake.

38.3 – Discuss the factors that predispose some people to become and remain obese. Anorexia Nervosa An eating disorder in which a person becomes significantly underweight (15%) Self-starvation diets, extreme exercise regimens and delusions Bulimia Nervosa An eating disorder characterized by episodes of overeating (high-caloric foods), followed by vomiting, laxative use, fasting or excessive exercise Characterized by weight fluctuations Binge-Eating Disorder