Mind, Brain & Behavior Friday March 7, 2003

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.

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.

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.

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.

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.

Motivation Chapter 33

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.

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.

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.

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.

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.

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.

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.

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)

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.

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).

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.

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.

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.

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

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.

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).

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.

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).

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.

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.

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.

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.

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

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

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

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.

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.