Hunger

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 BrainIn 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.

How does the hypothalamus work?

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?

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.

Are these disorders cultural?

Body Image

Level of Analysis for Our Hunger Motivation

Level of Analysis for Our Hunger Motivation

Level of Analysis for Our Hunger Motivation

Level of Analysis for Our Hunger Motivation

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

Calculate your BMI

Obesity

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

Weight Discrimination

Weight Discrimination

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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Definition Slide

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Definition Slides

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.

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

= the body’s resting rate of energy expenditure.

Anorexia Nervosa

= an eating disorder in which a person (usually an adolescent female) diets and becomes significantly (15 percent or more) underweight, yet, still feeling fat, continues to starve.

Bulimia Nervosa

= an eating disorder characterized by episodes of overeating, usually high-calorie foods, followed by vomiting, laxative use, fasting, or excessive exercise.

Binge-eating Disorder

= significant binge-eating episodes, followed by distress, disgust, or guilt, but without the compensatory purging, fasting, or excessive exercise that marks bulimia nervosa.

Sexual Response Cycle

= the four stages of sexual responding described by Masters and Johnson – excitement, plateau, orgasm, and resolution.

Refractory Period

= a resting period after orgasm, during which a man cannot achieve another orgasm.

Estrogens

= sex hormones, such as estradiol, secreted in greater amount by females than males and contributing to female sex characteristics. In nonhuman female mammals, estrogen levels peak during ovulation, promoting sexual receptivity.

Testosterone

= the most important of the male sex hormones. Both males and females have it, but the additional testosterone in males stimulates the growth of the male sex organs in the fetus and the development of the male sex characteristics during puberty.

Sexual Orientation

= an enduring sexual attraction toward members of either one’s own sex (homosexual orientation) or the other sex (heterosexual orientation).