Chapter 16 Motivation

Introduction

Types of behavior

– Unconscious reflexes and Voluntary Movements

– Motivation

• Driving force on behavior – Analogy– ionic driving force dependent upon many

factors • Probability and direction of behavior

– Vary with the driving force needed to perform the behavior

The Long-term Regulation of Feeding Behavior

Energy Balance– Prandial state - Anabolism: Energy storage as glycogen and

triglycerides– Postabsorptive state - Catabolism: Breaking down complex

macromolecules

The Long-term Regulation of Feeding Behavior

There are 4 different hypotheses related to feeding regulation:

Lipostatic Hypothesis - adipose tissue produces a humoral signal that is proportionate to the amount of fat in the body. This signal acts on the hypothalamus to decrease food intake and increase energy output. Much research into the hormone leptin relates to this hypothesis.

Gutpeptide Hypothesis - gastrointestinal hormones like gastrin releasing peptide (Grp), glucagons, or CCK. These hormones *may* inhibit food intake. Food entering the gastrointestinal tract triggers release of these hormones which act on the brain to produce satiety.

Glucostatic Hypothesis - the activity of the satiety center in the ventromedial nuclei is probably governed by the glucose utilization in the neurons. It has been postulated that when their glucose utilization is the activity across the neurons decrease. Under these conditions, the activity of the feeding center is unchecked and the individual feels hungry.

Thermostatic Hypothesis - according to this hypothesis, a decrease in body temperature below a given set point stimulates appetite, while an increase above the set point inhibits appetite.

Motivation and Feeding

Hormonal and Hypothalamic Regulation of Body Fat and Feeding

Body Fat and Food Consumption

– Lipostatic hypothesis

– Parabiosis

– Leptin

• Regulates body mass– Decreases appetite– Increases energy expenditure

– Leptin depletion

• Incites adaptive responses to fight starvation

Hormonal and Hypothalamic Regulationof Body Fat and Feeding

The Hypothalamus and Feeding

– Anorexia: lateral hypothalamic syndrome – lesions of this region lead to anorexia (see Bernardis, et.al.)

– Obesity: ventromedial hypothalamic syndrome

– Both related to leptin signaling

Hormonal and Hypothalamic Regulationof Body Fat and Feeding

• Response to Elevated Leptin Levels

Hormonal and Hypothalamic Regulationof Body Fat and Feeding

• Response to Decreased Leptin Levels

Harry Harlow – in 1967 received the National Medal of Science for his work on general human and child psychology. His work examined

motivation in monkeys.