Week 1: Stress and Adaptation

• Stress and Adaptation


  General Adaptation Syndrome: A non-specific response to noxious stimuli
• General Adaptation Syndrome


  1. Alarm

  2. Resistance

  3. Exhaustion
• Stress Response


  • Stimulation of the hypothalamic-pituitary-adrenal (HPA) axis
  • Reactive response occurs with both physical and psychological/emotional stressors
• Alarm


  Fight or flight - Sympathetic nervous system (SNS) response
• Resistance


  Normalization of the fight or flight response- Decrease SNS response
• Exhaustion


  Body can no longer restore homeostasis
• Reactive Response


  • Anticipatory response
  • Innate response - a predator, unfamiliar situations
  • Conditioned response
  • Experience-dependent memory programs
• Psychoneuroimmunology


  • All immune related disease is multifactorial
  • Immune modulation by psychosocial stressors lead directly to health outcomes
• Stress Response


  • Initiated by nervous & endocrine systems
  • Redirects blood flow, nutrients, & energy to areas that need it the most
  • Stimulation of the hypothalmic-pituitary-adrenal (HPA) axis
• HPA Axis


  1. Hypothalamus senses stressful stimulus

  2. Anterior pituitary releases adrenocorticotropic hormone (ACTH)

  3. Hypothalamus releases corticotropin-releasing hormone (CRH)

  4. Stimulation of Sympathetic Nervous System (SNS) and Adrenal Medulla

  5. Adrenal Cortex releases glucocorticoids (i.e. Cortisol)
• Catecholamines


  • Epinephrine and Norepinephrine
  • Norepinephrine released from sympathetic neurons directly into synaptic clefts near effector organs, including adrenal medulla
  • Epinephrine and some Norepinephrine are released from adrenal medulla
• Neurohormonal Mediators of Stress


  • Catecholamines - rapid, metabolize rapidly
  • Adrenocortical Steroids - slower, last longer
• Catecholamines


  • Epinephrine
  • Norepinephrine
• Adrenocortical Steroids


  • Cortisol (glucocorticoid)
  • Aldosterone (mineralocorticoid)
• Fight or Flight


  • Significant physiological implications
  • Significant implications for glucose metabolism and Na+ and water retention
• Fight or Flight


  1. ↑Blood Flow and glucose metabolism

  2. ↑Glycogenolysis, contraction, dilation of muscle vasculature

  3. ↓Glucose uptake and use (decreases insulin release)

  4. ↑Glucose production

  5. ↑gluconeogenesis

  6. ↓Blood flow

  7. ↑Lipolysis and ↓glucose uptake

  8. ↑Rate and Force of Contraction

  9. Peripheral Vasoconstriction

  10. Bronchodilation

  11. ↓Protein synthesis smooth muscle contraction and GI sphincter tone

  12. ↑Renin release
• Catecholamines Effect on Systems


  • Acute and Chronic Stress ↓NK cells
  • ↓Response of T cells and B cells
• Implications/Significance of Stress Response


  • Increased Na+ and water retention (with aldosterone & cortisol secretion)
  • Decreased urinary output
  • Weight gain
  • Increased ECF, cardiac workload and BP
  • Increased blood sugar
  • Increased gastric secretions with cortisol & decreased blood flow to gastrointestinal tract (ulcers)
  • Decreased inflammatory/immune response -> increased susceptibility to infection (impaired wound healing)
• Indicators of High Stress