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This file accompanies a YouTube clip. It distinguishes allostasis from homeostasis and provides a brief overview of the allostatic response and allostatic load - see facebook page for link to clip - (or website of same name)

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  1. 1. Homeostasis (homeo = stable)Key Points• Our internal states are constantly being disturbed & corrected• Specifically homeostasis involves continual regulation of vital body functions such as body temp, oxygen levels, blood-glucose levels, water content, ion content, etc to a level of balance• So the body takes corrective action e.g.. sweating to cool skin, shivering to warm the body• But the regulation of the body occurs Note: Body by a single point e.g. via alternation of blood oxygen levels (only) temperature• The body can only cope with minor can only vary variations i.e. it must operate within by 5-6% set limits in order to survive
  2. 2. Allostasis (Allo = variable; stasis = stand)Key Points• Achieves physiological or psychological stability through behavioral or physiological change• Thus the body can meet and copy with internal/ external demands• brain tells the body to maintain physiological stability by adapting to changes caused by stressor e.g. increase in HR – to enable our body to exercise (without the muscles being deprived of level of blood required for exertion)• Via the allostatic systems e.g. Autonomic.N.S, HPA axis, immune system, cardiovascular system, etc
  3. 3. Allostasis• Thus is a more dynamic & adaptive process (than homeostasis)• E.g. if dehydrated, sweat levels, kidneys, mucous membrane, eyes & nose all reduce output• Key point: the body can cope with large changes in response to changing conditions via both internal & external demands• So our body can function efficiently during variable states such as sleep/ exercise; quiet/ loud; hot/ cold; hunger/ full; isolation/ crowds; safe/ danger – via increase/ decrease in HR/ Blood pressure/ Respiration rate/ Note: Heart rate can increase by 250% for an adolescent (from a relaxed state to a state of high physical exertion
  4. 4. Allostatic responseAllostatic Response• Increases arousal in response to a stress – via HPA axis & sympathetic.N.S (thus is good in the short term) Allostatic response involves: Increase in Physiological arousal to deal with stressor i.e. activation of HPA axis When the stressor has been successfully dealt with: The Brain switches off the allostatic response to reduce the wear & tear on the body
  5. 5. Allostatic loadAllostatic Load (think of it as overLOAD)• Allostatic load refers to the Genetics cumulative cost to the body of allostasis• Excessive energy consumption Context during high stress times• Can diminish effectiveness of Allostatic response• Thus potentially triggering physiological/ psychological disorders• Thus the brains appraisal of the stressor plays a major role in the body’s response Appraisal –• As influenced by the based on biopsychosocial model experience