1. Introduction to Psychology Motivation and Control of Action Prof. Jan Lauwereyns jan@sls.kyushu-u.ac.jp jan@sls.kyushu-u.ac.jp

2. Homeostasis Definition – ‘Maintenance of the body’s internal environment within a narrow physiological range’ Internal environment – refers to body temperature and blood compositions

3. Hypothalamus Primarily involved in maintaining body temperature, fluid and energy homeostasis

4. Thirst Water regulation is critical: 70% of body is water – concentration of chemicals determines rate of reactions – blood volume must be enough to maintain blood pressure and circulation Strategies for regulation – too much: excess water excreted through urination – too little: vasopressin, anti-diuritic hormone, constricts blood vessels to increase blood pressure and enables kidneys to reabsorb water and secrete concentrated urine

5. Energy Balance Why is it important? Brain needs constant glucose supply A few minutes glucose deprivation leads to loss of consciousness and death Hunger

6. Biological needs The drive reduction hypothesis Think: Inclusive fitness (Darwinian processes) Think: energy, reproduction Approach Avoid

7. Biological needs Several hours have passed since last meal Increased drive (hunger) Increased exploratory activity Find food, eat it Drive is reduced (reinforcement) The drive reduction hypothesis

8. Biological needs Several hours have passed since last meal Find food, eat it Drive is reduced (reinforcement) The drive reduction hypothesis Increased drive (hunger) Increased exploratory activity

9. Biological needs Several hours have passed since last meal Find food, eat it Drive is reduced (reinforcement) The drive reduction hypothesis Increased drive (hunger) Increased exploratory activity Wanting Liking

10. When do you start (wanting) a meal? - Cultural and social factors (habit, copy) - Physiological factors (hunger)

11. Eating: Physiological factors Fuel for cells: – Glucose (brain) – Fatty acids (rest of the body) Glucose in a meal some used for fuel some converted into glycogen The glucostatic hypothesis of hunger

13. Neurons in the hypothalamus Lateral hypothalamus: –Neurons signal hunger (“glucostats”) –When damaged, no hunger, won’t eat, will starve

14. Glucose, Insulin and Glucagon Glucose – much of digested food enters bloodstream as glucose, primary energy source for cells in body and brain – remains constant because liver converts stored nutrients to glucose Amount of glucose actually available to cells depends on two hormones from pancreas – insulin helps glucose enter cells, decreasing amount in bloodstream – glucagon stimulates liver to convert glycogen to glucose, increasing amount in bloodstream

15. Neurons in the hypothalamus Lateral hypothalamus: –Neurons signal hunger (“glucostats”) –When damaged, no hunger, won’t eat, will starve Ventromedial hypothalamus: –Neurons signal satiation –When damaged, never enough, will keep eating, grow very obese

16. After a meal insulin levels rise and glucose enters cells, appetite decreases – as glucose levels fall, the pancreas releases glucagon and less insulin – less glucose for immediate fuel, blood levels rise and hunger returns

17. Untreated diabetics eat much but lose weight. Because of their low insulin levels, the glucose in their blood cannot enter the cells, either to be stored or to be used. Consequently, glucose is excreted in their urine, leaving the cells to starve.

18. When do we eat more than we need? – when we are with other people – in the evening – on weekends – if food is low-fat – when it tastes good – alcoholic beverages add calories Disorders – Anorexia nervosa, bulimia – Hormonal conditions (e.g., leptin)