Stress and Disease. Chapter 8. Elsevier items and derived items 2008 by Mosby, Inc., an affiliate of Elsevier Inc.

Transcription

1 Stress and Disease Chapter 8

2 Stress A person experiences stress when a demand exceeds a person s coping abilities, resulting in reactions such as disturbances of cognition, emotion, and behavior that can adversely affect wellbeing

3 Dr. Hans Selye Worked to discover a new sex hormone Injected ovarian extracts into rats Witnessed structural changes Ø Enlargement of the adrenal gland Ø Thymic and other lymphoid structure atrophy Ø Development of bleeding ulcers in the stomach and duodenal lining

4 Dr. Hans Selye Dr. Selye witnessed these changes with many agents. He called these stimuli stressors.

5 General Adaptation Syndrome (GAS) Dr. Selye termed this general response, the general adaptation syndrome (GAS)

6 General Adaptation Syndrome (GAS) Three stages Ø Alarm stage Arousal of body defenses Ø Stage of resistance or adaptation Mobilization contributes to fight or flight Ø Stage of exhaustion Progressive breakdown of compensatory mechanisms Onset of disease

7 GAS Activation Alarm stage Stressor triggors locus coeruleus in the brainstem, releases NE, has an excitatory effect on most of the brain, mediating arousal and priming the brain s neurons to be activated by stimuli. Stimulates the hypothalamus to release CRH Ø Then CRH triggers the hypothalamic-pituitaryadrenal (HPA) axis Resistance stage Ø Begins with the actions of adrenal hormones Exhaustion stage Ø Occurs only if stress continues and adaptation is not successful

8 Stress Response Nervous system Endocrine system Immune system : may enhance or suppress immune system, depends on intensity, type and length of time of the stressor

9 Psychologic Mediators and Specificity Reactive response: the physiological response to the actual stressor i.e sweating, racing heart during a test Anticipatory response: the same as above but is from just thinking about Monday s final yuck Conditional response: people screaming scares/startles a kid who was raised by violent parents

10 Neuroendocrine Regulation

11 Neuroendocrine Regulation Catecholamines Ø Released from chromaffin cells of the adrenal medulla Epinephrine and norepinephrine are released Ø α-adrenergic receptors α 1 and α 2 Ø β-adrenergic receptors β 1 and β 2 Ø Mimic direct sympathetic stimulation

12 Neuroendocrine Regulation Cortisol (hydrocortisone) Ø Activated by adrenocorticotropic hormone (ACTH) Ø Stimulates gluconeogenesis Ø Elevates the blood glucose level Ø Powerful anti-inflammatory and immunosuppressive agent

13 Cortisol and Immune System Glucocorticoids and catecholamines Ø Decrease cellular immunity while increasing humoral immunity Ø Increase acute inflammation and mobilize innate immune cells Ø Decrease in Th1 increase in Th2 lymphocytes Ø Light to moderate exercise (physical stress) can help one fight/prevent an infection if no fever. But intense and exhaustive exercise can suppress immunity overall because of high cortisol (marathon runners and after finals week)

14 Stress Response

15 Stress-Induced Hormone β-endorphins Alterations Ø Proteins found in the brain that have pain-relieving capabilities Ø Released in response to stressor Ø Inflamed tissue activates endorphin receptors Ø Hemorrhage increases levels, which inhibits blood pressure increases and delay compensatory changes

16 Stress-Induced Hormone Alterations Growth hormone (somatotropin) Ø Produced by the anterior pituitary and by lymphocytes and mononuclear phagocytic cells Ø Affects protein, lipid, and carbohydrate metabolism and counters the effects of insulin Ø Enhances immune function after acute stress Ø Chronic stress decreases growth hormone

17 Stress-Induced Hormone Prolactin Alterations Ø Released from the anterior pituitary Ø Necessary for lactation and breast development Ø Prolactin levels in the plasma increase as a result of stressful stimuli Ø Prolactin enhances innate and lymphocyte immunity only under stressed conditions

18 Stress-Induced Hormone Oxytocin Alterations Ø Produced by the hypothalamus during childbirth and lactation Ø Produced during orgasm in both sexes Ø May promote reduced anxiety Ø Known as the hormone of affection and nurturing, OT knock out mice mother s ignore their pups

19 Role of Immune System Stress directly related to proinflammatory cytokines Link between stress, immune function, and disease Immune system affected by neuroendocrine factors (cortisol, CRH, catecholamines, melatonin Stress response decreases T cell cytotoxicity and B cell function

20 Stress, Personality, Coping, and Illness A stressor for one person may not be a stressor for another Psychologic distress Ø General state of unpleasant arousal after life events that manifests as physiologic, emotional, cognitive, and behavior changes

21 Stress, Personality, Coping, and Illness

22 Stress impact on obesity CRH is a VERY strong satiety molecule and NE and E are appetite suppressants (diet pills have ingredients like E and NE).?? So how can people say that stress increases appetite??? Hint what happens to CRH as blood cortisol levels increase?