Mind, Brain & Behavior

1. Mind, Brain & Behavior Friday March 7, 2003

2. Stress and Anxiety • Stress is the response of the body to any demand. • Stress is not harmful. • Prolonged stress in a situation where one is helpless is harmful (lack of control). • Stress contributes to disease. • Cortisol is a measure of stress. • Stress changes brain chemistry.

3. Social Attachment • Emotional expressions generate empathy and regulate interpersonal behavior. • Social species have greater emotion. • Attachment permits essential learning. • Attachment permits individuals to regulate their affect (control emotion). • Attachment reduces stress.

4. Emotion Regulation • Anger motivates instrumental behavior to change things. • However, people must conform to social expectations about expression of anger. • Controlling emotion is not psychologically damaging but is what people must learn to do from infancy.

5. Venting is Ineffective • Staying angry is harmful. • Venting (expressing affect) is ineffective at decreasing or eliminating negative affect – if the person stays angry. • Venting prolongs negative affect. • Venting does not defuse hostility but escalates it in relationships. • Distraction helps.

6. Rumination & Perseveration • Perseveration – obsessively returning to thoughts about one’s problems. • Ruminating (brooding) prevents active problem solving. • Rumination decreases likelihood someone will engage in mood-changing activities. • Rumination biases thinking, leading to a vicious circle of depression.

7. Motivation Chapter 33

8. Homeostasis • Homeostasis -- keeping the internal environment of the body the same (constant) regardless of changes externally. • Accomplished by two systems: • Central nervous system (hypothalamus and brain stem) • Autonomic and diffuse enteric systems of the peripheral nervous system.

9. Purpose of Homeostasis • Maintains internal temperature. • Maintains blood sugar level. • Maintains balance of essential salts and minerals. • Maintains fluids (level of hydration) in cells and intracellular.

10. Autonomic Nervous System • Two parts: • Sympathetic • Parasympathetic • Includes sensor and effector components. • Sensors monitor internal functioning. • Effectors activate or inhibit target structures such as blood vessels or glands.

11. What Do Sensors Monitor? • Chemical variations in blood composition. • Tension changes in the vascular system (blood vessels). • Distension of the intestines, bladder and gall bladder.

12. Where Sensor Neurons Go • Sensor neurons from the viscera (visceral afferent nerves) go: • To the spinal cord • From spinal cord to ganglia in the sympathetic and parasympathetic systems. • Postganglionic fibers go to the targets. • ACh (acetylcholine) is the neurotransmitter for neurons from spinal cord to ganglia.

13. Sympathetic • Mobilizes body for “fight or flight” response. • In addition to direct NE (norepinephrine) to targets, adrenal medulla secretes NE in bloodstream to sympathetic targets. • Nicotine in cigarettes activates sympathetic nervous system.

14. Parasympathetic • Initiates rest and recuperation. • Activation comes from the brainstem. • Vagus nerve carries sensor and effector information from heart, lungs and intestines. • Preganglionic axons are very long. • Postganglionic fibers use ACh not NE – receptors are muscarinic (blocked by atropine) not nicotinic.

15. Comparison of Parts of the ANS • Different in function. • Preganglionic fibers emerge from different spots in the spinal cord. • Ganglia are in different places: • Close to organs for parasympathetic • Close to spinal cord for sympathetic • Postganglionic effectors use different neurotransmitters (NE vs ACh)

16. Coordination of the Systems • Systems are complementary -- both are active at the same time – not alternating. • What happens during anger? • Sympathetic arousal increases blood pressure. • Medulla detects that arousal and activates the parasympathetic to keep blood pressure within normal limits. • Hypertension occurs with deficient feedback.

17. Diffuse Enteric System • A third major division of the autonomic nervous system. • Neural control unit between the autonomic postganglionic nerves and the gastrointestinal system. • Contractions of muscles propels food through digestive system (peristalsis).

18. Central Regulation (CNS) • Hypothalamus – integrates visceral functioning: • Activates the autonomic nervous system • Regulates hormones secreted from the pituitary gland and thereby controls the endocrine system.

19. Three Parts of Hypothalamus • Periventricular Zone – regulates temperature, salt concentration, levels of hormones. • Medial Zone – produces vasopressin and oxytocin in posterior pituitary. • Lateral Zone – permits cortex and limbic system to over-ride hypothalamic activity, manages long-term regulation.

20. Medulla Oblongata • Responsible for monitoring: • Spontaneous respiratory movement (breathing) • Blood pressure • Cardiac rhythm • “Brain death” occurs with loss of hypothalamic and medullary control over respiration, lack of EEG waves.

21. Endocrine System • Endocrine organs include: • Pituitary gland • Adrenal Cortex • Gonads (ovaries and testes) • Thyroid and parathyroid • Adrenal cortex • Islet cells of pancreas • Secretary cells that line intestinal tract

22. Physiological Setpoints • Adaptive systems use feedback from sensors to maintain constant values (setpoints) for important properties. • Positive feedback activates a central controller • Negative feedback inhibits the controller.

23. Temperature Regulation • Two controls: • Sensors from skin • Blood temperature (at hypothalamus) • Heat-gain mechanisms increase blood temperature (goose bumps). • Heat-loss mechanisms decrease it (shunt blood to skin, perspiration).

24. Purpose of Fever • Occurs when immune response causes heat-gain mechanisms to increase body temperature. • Elevated temperature: • Activates antibody-producing cells • Increases the rate at which white blood cells move to sites of infection. • Directly affect some viruses but not all.

25. Blood Pressure • Pressure or baro-receptors measure pressure in the large arteries above the heart. • Excess pressure activates the medulla oblongata: • Excess sympathetic activity depressed. • Inhibition of vasomotor centers (which expand and contract blood vessels).

26. High Blood Pressure • Ongoing competition between sympathetic and parasympathetic. • Setpoints are too high in people with chronic high blood pressure. • Causes include: • Kidney disease • Overactive sympathetic system.

27. Appetite Control • Motivation to eat arises from a complex interplay of physiological mechanisms. • Two systems involved: • Metabolic need system – restore depleted energy • Caloric homeostasis system – eat when food is available until stomach is distended.

28. Setpoint Hypothesis of Eating • Adiposity (fat storage) may be a regulator of eating behavior. • The brain directs metabolic processes to maintain its fat store. • Insulin signals status of fat stores to the brain. • Adiposity affects insulin secretion. • Lean people are more sensitive to insulin so more carbohydrate is used and does not become fat.

29. Satiety Factors • Stretch receptors signal “fullness” to prevent overfilling of the stomach. • Digestive hormones secreted in the gut signal satiety. • Manipulation of these hormones can change eating behaviors and weight in mice.

30. Psychological Factors • Learned associations with time and place. • Socialization and rituals associated with food (e.g., eating at a party). • People eat more when in social situations. • Preferences and taste

31. Eating Disorders • Anorexia Nervosa – deliberate starvation due to psychological factors. • Insufficient body weight • Distorted body image, food obsession • Anorexics have normal appetite • Bulimia Nervosa – food binging followed by purging with laxatives or vomiting. • Normal body weight

32. Obesity • Based on height and weight, a body mass index above 30 (above 25 is overweight). • http://www.caloriecontrol.org/bmi.html • Causes: • Different metabolic rate • Larger adipocytes • More vulnerable to food cues, finicky • Recidivism after dieting = 90+% in all forms of treatment.

33. Sexual Behavior • Phases of sexual response are the same across species. • Behavior results from many circuits, including hypothalamic activation, environmental inputs, hormones. • The cortex decides what is and is not sexually stimulating.

34. Homosexuality • Defined as sexual attraction to members of the same sex. • Large-scale studies show that neither early childhood experiences nor learning accounts for homsexuality. • Postmortem studies suggest the SCN of the hypothalamus may be responsible.