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Topic 17 Motivation Lange

Topic 17 Motivation Lange. Biology 463 - Neurobiology. Introduction. Behavior can be subdivided into Unconscious Reflexes Voluntary Movements Motivation is the driving force behind many behaviors. For example, hunger is a motivation that elicits a desire to eat.

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Topic 17 Motivation Lange

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  1. Topic 17 Motivation Lange Biology 463 - Neurobiology

  2. Introduction Behavior can be subdivided into • Unconscious Reflexes • Voluntary Movements Motivation is the driving force behind many behaviors. For example, hunger is a motivation that elicits a desire to eat. Motivation has roots in physiology and also behavioral/cognitive neuroscience. Biologically, motivation may be thought of as a drive evolutionarily designed to optimize well-being, minimize physical pain and/or maximize pleasure. Motivation can and often does originate from specific physical needs such as eating, sleeping or resting, and sex.

  3. 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.

  4. Harry Harlow’s work: • An American psychologist • He is best known for his maternal-separation, dependency needs, and social isolation experiments on rhesus monkeys all of which are associated with the study of motivation. • His work demonstrated the importance of care-giving and companionship in social and cognitive development. • recent work (not by Harlow) in rats have found evidence that touch during infancy have resulted in a decrease in corticosteroid, a steroid hormone involved in stress, and an increase in glucocorticoid receptors in many regions of the brain • (see Jutapakdeegul et.al., 2003)

  5. 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

  6. The Long-term Regulation of Feeding Behavior

  7. Motivation and Feeding 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 – alternative hormones that *may* inhibit food intake. Gastrointestinal hormones like gastrin releasing peptide (Grp), glucagons, or Cholecystokinin (CCK). In this hypothesis, 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 centers in the ventromedial hypothalamic nuclei are potentially governed by the glucose utilization in the neurons. The hypothesis suggests that when glucose utilization is high the activity across neurons decrease. Under these conditions, activity of the feeding centers 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.

  8. Hormonal and Hypothalamic Regulation of Body Fat and Feeding Body Fat and Food Consumption • Lipostatic hypothesis • Parabiosis (study method frequently used in studies) • Leptin • Regulates body mass • Decreases appetite • Increases energy expenditure • Leptin depletion • Incites adaptive responses to fight starvation

  9. Hormonal and Hypothalamic Regulationof Body Fat and Feeding The Hypothalamus and Feeding • Anorexia: lateral hypothalamic lesions of this region lead to anorexia • Obesity: ventromedial hypothalamic lesions lead to obesity • Both situations above may relate to leptin signaling (see Bellinger & Bernardis, 2002.)

  10. Hormonal and Hypothalamic Regulationof Body Fat and Feeding • Leptin is an adipokine that plays a key role in regulating energy intake and expenditure, including appetite, hunger, metabolism, and feeding behavior. • It is one of the most abundant adipose-derived hormones. • The Ob(Lep) gene (Ob for obese, Lep for leptin) is located on chromosome 7 in humans • Response to Elevated Leptin Levels In this high leptin situation, the arcuate nucleus will stimulate the PVN and inhibit the lateral hypothalamus to inhibit feeding (high leptin is associated with high adipose activity).

  11. Hormonal and Hypothalamic Regulationof Body Fat and Feeding • Response to Decreased Leptin Levels In this low leptin situation, the arcuate nucleus will inhibit the PVN and stimulate the lateral hypothalamus to encourage feeding (low leptin is associated with low adipose activity).

  12. END.

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