Homeostasis and Stress Adaptation

Flashcards on Homeostasis and Adaptive Responses to Stressors

Homeostasis

Remaining stable; 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 and endocrine system; a dynamic process that maintains or re- establishes homeostasis in light of environmental and lifestyle changes

Stress

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) Stages

Alarm, Resistance/Adaptation, Exhaustion

Alarm Stage

Fight-or-flight response due to stressful stimulus via the Hypothalamic-pituitary-adrenal (HPA) axis

Resistance or Adaptation Stage

Nervous and endocrine system mechanisms, returning the body to homeostasis or stability

Allostatic State

Activity of various systems attempting to restore homeostasis

Exhaustion/Allostatic Overload

The body can no longer return to homeostasis; “cost” of body’s organs and tissues for an excessive or ineffectively regulated allostatic response; effect of “wear and tear” on the body

Stressors

Agents or conditions that endanger homeostasis; may be external or internal; physical, chemical, biological, social, cultural or psychological; vary in scope, intensity, and duration

Risk Factors

Factors that are not stressors themselves, but are conditions or situations that increase the likelihood of encountering a stressor

Catecholamines

Play an integral role in allostasis in the classic model of homeostasis; Sympathico-adrenal system response mediates the fight-or-flight response; Examples: Norepinephrine and epinephrine

Effects of Norepinephrine

Constriction of blood vessels and an increase in blood pressure; reduction in gastric secretion; increase in night vision due to pupil dilation

Effects of Epinephrine

Enhances myocardial contractility, increases heart rate, and increases cardiac output; causes bronchodilation; increases the release of glucose from the liver (glycogenolysis) and elevates blood glucose levels

Adrenocortical Steroids

Cortisol and aldosterone; critical to maintenance of homeostasis; may synergize or antagonize effects of catecholamines

Effects of Cortisol

Principal glucocorticoid; affects protein metabolism; increases gluconeogenesis by the liver; promotes appetite and food-seeking behaviors; has anti-inflammatory effects

Effects of Aldosterone

Principal mineralocorticoid; promotes reabsorption of sodium and water by the kidney; increases blood pressure

Endogenous Opioids

Body’s natural pain relievers; raise pain threshold; produce sedation and euphoria

Immune Cytokines

Secreted by macrophages during stress response; enhance immune system response; prolonged stress can suppress immune functioning; Example: Interleukin-1

Adaptation and Coping

Adaptation: biopsychosocial process of change in response to new or altered circumstances, internal or external in origin. Coping: behavioral adaptive response to a stressor using culturally based coping mechanisms

Exhaustion/Allostatic Overload

Inadequate adaptation mechanisms or excessive allostatic load; results in inability to maintain homeostasis. Leads to various illnesses and disorders, both physical and emotional. Chemical mediators from the stress response contribute to various illnesses: cortisol, catecholamines, cytokines