L7 - Stress hormone axis

• What is the focus of the study material?

  Stress hormone axis overview
• What does stress threaten in an organism?

  Dynamic equilibrium (homeostasis)
• Who is the author of “Why Zebras Don’t Get Ulcers”?

  Robert Sapolsky
• What is the general adaptation syndrome based on?

  Work of Hans Selye
• What are the three phases of the stress response?

  Alarm, resistance, exhaustion
• What occurs during the alarm phase of stress response?

  • Initial response to stressor
  • Release of stress hormones
  • Activation of brain centers
• What happens during the resistance phase of stress response?

  • Adjustment leading to compensation
  • Activation of HPA axis
  • Release of cortisol
• What characterizes the exhaustion phase of stress response?

  • Prolonged stress exposure
  • Decreased growth and reproduction
  • Increased vulnerability to disease
• What is the primary stress response?

  Release of stress hormone from adrenal gland
• What activates the sympathetic outflow during stress response?

  Brain centers in the hypothalamus
• What hormones are released during the primary stress response?

  Epinephrine and norepinephrine
• What is the turnover time for catecholamines?

  Less than 10 minutes
• What is the role of the HPA axis in stress response?

  Responsible for cortisol release
• What is the turnover time for cortisol?

  Less than 30 minutes
• What are the secondary stress response effects?

  • Metabolic: energy mobilization
  • Cellular: increased HSP
  • Immune: antibody production
• What are the tertiary stress response effects?

  • Long-term changes in performance
  • Decreased growth and reproduction
  • Increased disease vulnerability
• Where are the adrenal glands located?

  Superior part of the kidney
• What are the two parts of the adrenal gland?

  Adrenal cortex and adrenal medulla
• What type of cells are chromaffin cells?

  Modified postganglionic sympathetic neurons
• What hormones are produced by chromaffin cells?

  Epinephrine and norepinephrine
• What is the fight-or-flight response associated with?

  Catecholamines from adrenal medulla
• From what are catecholamines synthesized?

  Tyrosine
• How are catecholamines stored?

  In chromaffin granules
• How do water-soluble hormones act?

  On cell surface receptors
• What type of receptors do adrenergic receptors belong to?

  G protein-coupled receptors
• What is the effect of β1 adrenergic receptors?

  Increase heart rate and contraction force
• What is the effect of β2 adrenergic receptors?

  Vasodilation in arterioles
• What are the functions of the adrenal cortex layers?

  • Glucocorticoids: regulate metabolism and stress resistance
  • Mineralocorticoids: modulate Na+ and K+ homeostasis
  • Androgens: contribute to secondary sexual characteristics
• What is cortisol synthesized from?

  Cholesterol
• How does cortisol act on target tissues?

  Through intracellular receptors
• What happens when cortisol binds to glucocorticoid receptors?

  Regulates mRNA transcription
• How is the HPA axis controlled?

  By negative feedback
• What effect do high cortisol levels have on the HPA axis?

  Inhibit HPA axis activity
• What are the key concepts to check your knowledge about stress?

  • Definition of stress
  • General adaptation syndrome
  • Primary, secondary, tertiary stress responses
  • Structures for hormone synthesis
  • Mechanisms of hormone action
  • Regulation of HPA axis
• True or False: Catecholamines are the main hormones during the resistance phase?

  False
• True or False: High cortisol levels can harm growth?

  True
• True or False: Cortisol is released from the adrenal medulla?

  False
• True or False: Both branches of the stress axis start with pituitary activation?

  False
• True or False: Catecholamines are synthesized in the adrenal medulla?

  True
• True or False: Cortisol is released by corticotropin-releasing hormone?

  False