Stress and Adaptation

homeostasis

a state in which all body systems are in balance at an ideal “set point”

Allostasis

ability to successfully adapt to challenges

• body undergoes variety of physiologic adjustments that help to reestablish homeostasis in response to environmental or behavioral changes

stress

tension of body or mind

stressors

agents that can produce stress and endanger homeostasis

• external or internal

• physical, chemical, emotional, biological, social, or cultural

• vary in scope, intensity, and duration

• individual reactions to stress can vary

• threat to homeostasis can be real or perceived

General Adaptation Syndrome (GAS) stages

• alarm reaction

• stage of resistance or adaptation

• stage of exhaustion

alarm reaction

• GAS stage

• stressful stimulus induces fight or flight response

  • hypothalamus pituitary adrenal axis activation

stage of resistance or adaptation

• GAS stage

• increased activity of the nervous system and the endocrine system to return the body to homeostasis

  • allostasis

Allostasis

refers to the activity of various systems in attempting to restor homeostasis

stage of exhaustion

• GAS stage

• prolonged stress —> depletion of resources/inability to adapt —> vulnerability to illness/inability to return to homeostasis

  • allostatic overload

Allostatic overload

• “coast” of body’s organs and tissues for an excessive or ineffectively regulated allostatic response; effect of “wear and tear” on the body

• inadequate that can lead to a disease or eventual death

Neurohormonal Mediators of Stress and Adaptation

• catecholamines

  • norepinephrine

• adrenocortical steroids

  • epinephrine

• endorphins and enkephalins

• oxytocin

catecholamines

• released by adrenal medulla as part of fight-or-flight response

• contains norepinephrine and epinephrine as physiologic effects

norepinephrine

physiological effect of catecholamines:

• constricts blood vessels

• raises blood pressure

• reduces gastric secretions

• increases night and far vision by dilating pupils (mydriases)

  • when things goes wrong, the GI tract loses

epinephrine

physiological effect of catecholamines:

• enhances heart muscle contractility

  • increases cardiac output

  • dilates airways to get some aire

  • increases release of glucose from liver

    • get some burst of energy/fuel

  • increases blood glucose level

adrenocortical steroids

contains cortisol and aldosterone

cortisol

• physiological effect of adrenocortical steroids (adrenal gland)

• increases blood glucose level

• energy burst

• promotes appetite and food seeking behaviors

• has anti-inflammatory effects

• prolonged-elevation —> immune suppression

aldosterone

• physiological effect of adrenocortical steroids (adrenal gland)

• promotes reabsorption of sodium and water in the kidney (instead of peeing gout sodium, under stressful conditions it will reabsorb it and keep it)

  • increases/helps maintain blood volume

  • increases blood pressure

  • maintains/increases perfusion of vital organs and skeletal muscle

endorphins and enkephalins

• endogenous opioids (body’s natural pain relivers)

  • raise pain threshold

  • produces euphoria and sedation

oxytocin

• produced during childbirth, lactation, sex

• calming effect, promotes human bonding, may moderate stress response

Immune cytokines

• secreted by macrophages during stress response

  • enhances immune system response

  • prolonged stress can suppress immune functioning

• ex) interleukin-1

individual stress response

can change with time and circumstances, influenced by culture, prior exposures

adaptation

biophysical change in response to new circumstance

coping

behavioral adaptive response (functional or dysfunctional)

distress

perceived inability to cope with a stressor