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 by a single point e.g. via alternation of blood oxygen levels (only)

• The body can only cope with minor variations i.e. it must operate within set limits in order to survive

Note: Body temperature can only vary

by 5-6%

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

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

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:

When the stressor has been successfully dealt with:

Increase in Physiological arousal to deal with stressori.e. activation of HPA axis

The Brain switches off the allostatic response to reduce the wear & tear on the body

Allostatic loadAllostatic Load (think of it as overLOAD)• Allostatic load refers to the

cumulative cost to the body of allostasis

• Excessive energy consumption 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

• As influenced by the biopsychosocial model

Context

Genetics

Appraisal – based on

experience