Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
PHYSIOLOGY OF STRESS Physiology III, Tri 4 Mrs. Brashear Resources for this lecture topic: Medical Physiology, Guyton & Hall Human Physiology, Vander Physiological Basis of Medical Practice, Best & Taylor Physiology, Berne & Levy Handbook of Stress, Medicine & Health, Cooper (Library) Objectives: 1. To define stress. 2. To learn the types of responses to stress. 3. To understand the acute stress response. 4. To understand the pathology of chronic stress. 5. To review stress management I. Stress defined A. Organism’s reaction to every kind of strain, challenge or demand which elicits a physiological response. B. Types of stress 1. physical trauma 2. prolonged exposure to cold 3. prolonged heavy exercise 4. infection 5. decreased oxygen supply 6. pain 7. fright 8. emotional stress 9. shock II. Responses to Stress A. Emotional reactions 1. anxiety 2. depression 3. apathy 4. alienation 5. hypochondriasis 6. etc. B. Behavioral reactions 1. smoking 2. drinking 3. taking risks 4. aggressive behavior 5. antisocial behavior C. Physiological reactions 1. Integrated response to stress that is protective a. mental b. physical 2. Neuroendocrine response a. Sympathetics b. Adrenal cortex and medulla III. Acute Stress Response Allows survival under numerous adverse conditions A. Function of Stress response B. Role of a Mass Sympathetic Response (Guyton, page 778) “fright or flight” = alarm or stress reaction MASS SYMPATHETIC RESPONSE (PARASYMPATHETIC INHIBITION) Sympathetic Stimulation Norepinephrine receptors -1 receptors action: action: vasoconstriction of vascular smooth muscle heart rate contractility conduction velocity Adrenal Glands Norepinephrine Epinephrine receptors High levels: vasoconstriction 1. Role of hypothalamus 2. Widespread reaction 3. Intent 4. Mechanisms: a. cardiac b. blood c. ventilation d. coagulation of blood e. muscle f. muscle and liver glycogenolysis g. mental alertness C. Role of the Hypothalamic-Pituitary-adrenocortical axis Or the CRH-ACTH-cortisol axis 1. Hormones involved a. ACTH b. catecholamines c. ADH -2 receptors Normal levels: vasodilatation d. angiotensin e. aldosterone f. glucagon g. GH h. cortisol 2. Stress syndrome pathway a. Hypothalamus Pituitary (CRH) (ACTH) Hypothalamus adrenocortical axis (cortisol) CRH Anterior Pituitary STRESS ACTH Adrenal Cortex cortisol INPUT FROM OTHER BRAIN AREAS HYPOTHALAMUS CRH SECRETION PLASMA CRH ANTERIOR PITUITARY ACTH SECRETION PLASMA ACTH ADRENAL CORTEX CORTISOL SECRETION PLASMA CORTISOL TARGET CELL OF CORTISOL RESPONSE TO CORTISOL b. General function of the axis STRESSORS STRESS SIGNALS Cortex, limbic system, reticular formation Hypothalamus norepinephrine neurons CRH neurons CRH neurons Cortisol Sympathetic neurons Pituitary Spinal Cord ACTH adrenal gland Arousal, behavioral Cortex Cortisol Medulla Epinephrine activation aggressiveness Feeding and sexual activity Excitatory Inhibitory Growth and reproductive function Local injury + energy mobilization & redistribution CV responsiveness to norepinephrine Mental changes Increased awareness of pain Energy mobilization redistribution cardiovascular responsiveness Inflammation Immune response Visceral function - Feeding, growth sexual activity, reproduction inflammation & immune response visceral function D. Effects of Cortisol during stress Normal homeostasis – Stress – Food Calories ADIPOSE TISSUE Triglycerides Lipolytic hormones Insulin Free Fatty Acids Glucose The effect of cortisol on the overall flow of fuels. Glycogen Glucose P Liver Glucose precursors Insulin Glucose Amino Acids Muscle Protein 1. Energy mobilization and redistribution a. protein metabolism – catabolism synthesis effect on muscles b. glucose metabolism inhibition of glucose uptake gluconeogenesis glycogen synthesis c. Lipids lipolysis 2. Cardiovascular function enhanced cardiac function enhanced vascular reactivity decreased endothelial permeability 3. Fluid volume ADH Aldosterone 4. Inflammatory response blocks prostaglandin production a. decreases vasodilation b. decrease permeability of membranes c. decrease migration of monocytes and lymphocytes blocks leukotrienes d. decrease in neutrophil function e. decrease in phagocytosis and bacterial killing Inflammatory Response production of Platelet activating Phosphatidyl choline Nitric oxide Arachidonic acid Prostaglandins Vasodilation Leukotrienes Neutrophil function Permeability Leukocyte trapping = Inhibition by cortisol 5. Immune Response – a. decrease in cellular and humoral immunity b. decrease in interleukin 1 & 6 c. decrease tumor necrosis factor Immune Response Macrophage Antigen Phagocytosis Bacterial killing = Inhibition by Cortisol Interleukin -1 Fever T - cells Tumor necrosis factor Interleukin -2 & 6 T-cell proliferation B-cell proliferation Antibody production 6. GH and sex steroids 7. Thyroid hormones IV. Chronic Stress Response Chronic stress can lead to syndromes and/or pathologies based on behavioral, neuroendocrine, autonomic and immunologic adaptation during stressful situations A. Physiological Changes Resulting from Chronic Stress 1. Endocrine-metabolic a. catabolic activity - cholesterol and fatty acids b. hyperglycemia c. insulin secretion related to hyperglycemia d. appetite – weight gain e. cellular activity and repair 2. GI tract a. mucosal protective barrier b. colonic motility 3. Musculoskeletal a. decreased lean body mass b. osteoporosis osteoblasts calcium absorption fibroblast activity c. skin d. growth and maturation in children 4. Capillary fragility 5. Immunity a. shrinkage of the thymus b. wound healing c. leukocytes d. suppression of 3 inflammatory cytokines B. Linking Stress to Disease Causative? Increased activity in genetic tendencies? 1. muscle tension 2. GI symptoms indigestion, vomiting, heartburn, irritable colon syndrome, constipation, etc. 3. CV symptoms arrhythmias, CAD, pain or tightness, palpitations, hypertension, stroke sudden death 4. Respiratory dyspnea and hyperventilation 5. CNS insomnia, weakness, fatigue syndromes, faintness & headaches 6. Mental disorders such as anxiety, depression 7. Decreased Immune response infection latent oncogenic viruses metastatic spread of cancer cells newly transformed cancer cells 8. Sexual dysfunction dysmenorrhea frigidity and impotence 9. Dermatological problems V. Stress Management 3 basic pathways in order of preference A. Eliminate or modify stress producing situation or remove individual B. Change social situation C. Strengthen the person to stress 1. physical exercise 2. meditation 3. relaxation techniques 4. social support VI. Use of cortisol medically A. Anti-inflammatory B. Side effects