I. The Motivation of Hunger and Eating
A. Introduction
1. Motives are the needs, wants, interests and desires that propel people in certain directions.
2. Motivation involves goal-directed behavior.
3. There are 2 types of motivation – biological motives that originate in biological needs (i.e. hunger), and social motives, that originate in social experiences (i.e. achievement).
4. People share the same biological needs, but their social needs (and their strengths) may vary.
B. Biological Factors in the Regulation of Hunger
1. Brain Regulation – experience of anger is controlled in the brain, specifically 2 areas in the hypothalamus.
a. Hypothalamus – tiny structure involved in the regulation of a variety of biological needs related to survival.
b. Lateral hypothalamus (LH) & the ventromedical nucleus of the hypothalamus (VMH) regulate hunger, but not the key elements.
c. 3rd area of hypothalamus, known as the paraventricular nucleus (PVN) may play role in hunger regulation.
d. Contemporary theories of hunger focus more on neural circuits rather than anatomical centers of the brain.
2. Glucose and Digestive Regulation
a. Glucose – a simple sugar that is an important source of energy.
i. Mayer – proposed that hunger is regulated by the rise and fall of blood glucose levels. ii. Glucostic Theory – proposed that fluctuations in blood glucose level are monitored by glucostats – neurons sensitive to glucose in the surrounding fluid.
b. Digestive system – nerves send signals that inhibit further eating by monitoring stretching of stomach walls or carry messages that depend on how rich in nutrients the contents of the stomach are.
3. Hormonal Regulation – appear to contribute to regulation of hunger.
a. Insulin – hormone secreted by the pancreas which much be present for cells to extract glucose from the blood.
b. Leptin - produced by fat cells throughout the body and released into the bloodstream. High levels of fat produce high levels of leptin, and circulates through the bloodstream, providing the hypothalamus with info about the body’s fat stores.
C. Environmental Factors in the Regulation of Hunger
1. Hunger is a biological need, but eating may in some instances be social, and influenced by 3 factors – learned prefs/habits, food related cues, and stress.
2. Learned Prefs and Habits – People from different cultures display very different patterns of food consumption.
a. Prefs for high fat foods.
b. Taste prefs are partly a function of learned associations formed through classical conditioning.
c. Eating habits are shaped by observational learning – people prefer familiar foods, or the reactions of others around them.
d. May also dictate when and how much people eat.
3. Food Related Cues – hunger can be influenced by exposure to environmental cues that have been associated with eating.
4. Stress, Arousal, and Eating – Stress may lead to increased eating.
D. Eating and Weight: The Roots of Obesity
1. Obesity 0 the condition of being overweight. May occur due to abandonment of diet followed by early humans.
2. Genetic Predispotion may cause obesity.
a. BMI – body mass index – weight in kilos, divided by height in meters, squared (kg/m^2).
3. The Concept of a Set Point – body may have a set point, or natural point range of stability in body weight.
4. Dietary Restraint – chronic dieters are restrained eaters – people who consciously work overtime to control their eating impulses and who feel guilty when they fail.
5. When their cognitive control is disrupted, they become disinhibited and eat excessively.
II. Sexual Motivation and Behavior
A. Determinants of Sexual Desire
1. Sex is essential for the survival of a species, but not essential to an individual’s survival.
2. Sexual desire is influenced by a complicated network of biological and social factors.
3. Hormonal Regulation – may have a small impact on sexual desires.
a. Hormones secreted by the gonads can