Pathophysiology Notes: Modules 1, 2, & 3

Module 1 Chapter 2: Homeostasis, Allostasis, and Adaptive Responses to Stressors Homeostasis & Allostasis Homeostasis:  Remaining stable while staying the same  A state in which all systems are in balance  A sta ...

Module 1 Chapter 2: Homeostasis, Allostasis, and Adaptive Responses to Stressors Homeostasis & Allostasis Homeostasis:  Remaining stable while staying the same  A state in which all systems are in balance  A state of equilibrium  An ideal “set point” despite alterations within the body Allostasis:  Ability to successfully adapt to challenges  Intricate regulatory processes orchestrated by the brain  A dynamic process that maintains or re-establishes homeostasis in light of environmental and lifestyle changes Stress As A Concept  Physical, chemical, or emotional factor resulting in tension of body or mind  Actual physical and mental state that tension produces  Real or perceived threat to homeostasis  Direct consciously or indirect unconsciously sensed threat to the stability of the organism  Physical, chemical, or emotional factor resulting in tension of body or mind  Actual physical and mental state that tension produces  Real or perceived threat to homeostasis  Direct consciously or indirect unconsciously sensed threat to the stability of the organism General Adaptation Syndrome (GAS) (Selye)  Three stages: Alarm, resistance/adaption, and exhaustion  Alarm stage: fight-or-flight response as the result of stressful stimulus  Hypothalamic-pituitary-adrenal (HPA) axis  Resistance/adaptation: activity of the nervous and endocrine systems in returning the body to homeostasis  Allostatic state: activity of various systems attempting to restore homeostasis  Exhaustion: point where body can no longer return to homeostasis  Allostatic overload: “cost” of body’s organs and tissues for an excessive or ineffectively regulated allostatic response; effect of “wear and tear” on the body Fig. 2-2; P. 15 P. 16  Stressors  Agents or conditions that can produce stress; endanger homeostasis  May be external or internal  External examples: school, work, life event (wedding)  Internal examples: cancer, child birth/pregnancy  Physical, chemical, biological, social, cultural or psychological  Physical: hand injury  Social: standing in front of a class  Cultural: acceptance/ability to practice  Vary in scope, intensity, and duration  Reactions to stress vary depending upon genetic constitution, gender, past experiences, cultural influences, developmental stage, and age  Past experience: a child afraid of a playground b/c he was previously abused there  Can include both negatively and positively perceived events  Risk Factors: Not stressors, but conditions or situations that increase the likelihood of encountering a stressor; there is some control over our stressors  Neurohormonal Mediators of Stress & Adaption  Catecholamines  Play an integral role in allostasis  Symphathico-adrenal system response mediates the fight or flight response  Examples: Norepinephrine and epinephrine  Norepinephrine  Constricts blood vessels and raises blood pressure  Reduces gastric secretions  Epinephrine  Enhances myocardial contractibility, increases heart rate, and increases cardiac output  Causes bronchodilation  Increase the release of glucose from the liver (glycogenolysis) and elevates blood glucose levels  Adrenocortical Steroids  Critical to maintenance of homeostasis  May synergize or antagonize effects of catecholamines  Examples: Cortisol and aldosterone  Cortisol  Primary glucocorticoid  Affects protein metabolism  Promotes appetite and food-seeking behaviors  Had anti-inflammatory effects  Too much cortisol over time can lead to pro-inflammatory effects  Aldosterone (secreted by the adrenal cortex)