The Physiology of Hunger • Contractions of the stomach • Washburn study
Physiology of Hunger • Washburn’s studies showed hunger was partially related to the stomach. • But those with their stomachs removed still feel hunger.
Body Chemistry • Glucose • The hormone insulin converts glucose to fat. • When glucose levels drop- hunger increases.
The Physiology of HungerBody Chemistry and the Brain • Glucose • Insulin • Hypothalamus • Lateral hypothalamus • orexin • Vetromedial hypothalamus
The Brain In the 1960’s it was discovered that hunger comes from……….. The Hypothalamus
The Hypothalamus & Hunger • Along the sides of the hypothalamus is the lateral hypothalamus: which brings on hunger. Stimulate the lateral hypothalamus and even a well fed animal will begin to eat. Lesion the lateral hypothalamus and a starving animal will have no interest in food.
The Hypothalamus and Hunger • Along the lower middle section of the hypothalamus is the ventromedial hypothalamus: which depresses hunger. Stimulate the ventromedial hypothalamus and the animal will stop eating Lesion the ventromedial hypothalamus the animal will continuously want to eat.
Leptin Leptin is a protein produced by bloated fat cells. Hypothalamus senses rises in leptin and will curb eating and increase activity. Can leptin injections help me? Set Point Hypothalamus acts like a thermostat. We are meant to be in a certain weight range. When we fall below weight our body will increase hunger and decrease energy expenditure (Basic Metabolic Rate). What happens if we go above our set point? How does the hypothalamus work? Two Theories
The Physiology of HungerBody Chemistry and the Brain • Appetite hormones • Ghrelin • Obestatin • PYY • Leptin • Set point • Basal metabolic rate
The Appetite Hormones • Insulin: Hormone secreted by pancreas—controls blood glucose. • Leptin: Protein secreted by fat cells—when abundant, causes brain to increase metabolism and decrease hunger. • Orexin: Hunger-triggering hormone secreted by hypothalamus. • Ghrelin: Hormone secreted by empty stomach—sends “I’m Hungry” signals to the brain. • Obestatin: Sister hormone to ghrelin. Secreted by stomach—sends “I’m Full” signals to the brain. • PYY: Digestive tract hormone—sends “I’m Not Hungry” signals to the brain.
The Psychology of HungerTaste Preferences: Biology and Culture • Taste preferences • Sweet & Salty: Genetic & Universal • Neophobia: fear of trying new and unfamiliar—extends to foods • Adaptive taste preferences
The Psychology of HungerEating Disorders • Eating disorders • Anorexia nervosa • Bulimia nervosa • Binge-eating disorder
Eating Disorders Anorexia Nervosa • An eating disorder in which a normal weight person diets and becomes significantly underweight, yet, still feeling fat, continues to starve.
Eating Disorders Bulimia Nervosa • An eating disorder characterized by episodes of overeating, usually of high caloric foods, followed by vomiting, laxative use, fasting, or excessive exercise.
Obesity and Weight Control • Historical explanations for obesity • Obesity • Definition (BMI 30 & ↑) • Statistics • Adult obesity, 34%(more than doubled in last 40 yrs) • Child-teen obesity has quadrupled • Obesity and life expectancy
Obesity • Severely overweight to the point where it causes health issues. • Mostly eating habits but some people are predisposed towards obesity. Click on the pictures to see some case studies on obesity.
Obesity and Weight ControlThe Social Effects of Obesity • Social effects of obesity • Weight discrimination • Psychological effects of obesity
Obesity and Weight ControlThe Physiology of Obesity • Fat Cells We store energy in fat cells, which become larger & more numerous if we are obese, and smaller (but still more numerous) if we then lose weight.
Obesity and Weight ControlThe Physiology of Obesity • Set point • Metabolism • Once we become fat, we require less food to maintain our weight • Fat tissue has a lower metabolic rate • Overweight person’s weight drops below previous set point, hunger ↑ and metabolism ↓ • Body adapts to starvation by burning off fewer calories
Obesity and Weight ControlThe Physiology of Obesity • The genetic factor • The food and activity factor • Sleep loss • Social influence • Food consumption and activity level
Obesity and Weight ControlLosing Weight • Realistic and moderate goals • Success stories • Attitudinal changes
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Division title (green print)subdivision title (blue print) Use this slide to add a table, chart, clip art, picture, diagram, or video clip. Delete this box when finished
Definition Slide = add definition here
Motivation = a need or desire that energizes and directs behavior.
Instinct = a complex behavior that is rigidly patterned throughout a species and is unlearned.
Drive-reduction Theory = the idea that a physiological need creates an aroused tension state (a drive) that motivates an organism to satisfy the need.
Homeostasis = a tendency to maintain a balanced or constant internal state; the regulation of any aspect of body chemistry, such as blood glucose, around a particular level.
Incentive = a positive or negative environment stimulus that motivates behavior
Hierarchy of Needs = Maslow’s pyramid of human needs, beginning at the base with physiological needs that must first be satisfied before higher-level safety needs and then psychological needs become active.
Glucose = the form of sugar that circulates in the blood and provides the major source of energy for body tissues. When its level is low, we feel hunger.