Pathophysiology of Stress

Definition of Stress

• Coined by Hans Selye as "the non-specific response of the body to any demand placed on it."
• Body's response to harmful threats affecting normal body functioning.

Effects of Stress on Systems

Nervous System

• Autonomic Nervous System
  • Activates the sympathetic portion.
  • Secretes epinephrine (adrenalin) leading to "fight or flight" response:
    • Increased heart rate and blood pressure.
    • Increased breathing rate.
    • Pupil dilation.
    • Increased blood flow to muscles, lungs, and heart.
    • Decreased digestion.
• Cerebral Cortex
  • Increases processing of the threat with focus, planning, and attention.
• Thalamus
  • Enhances sensory input (hearing, vision, smell).
• Hypothalamus
  • Secretes stress-related hormones.
• Limbic System
  • Produces emotional responses (anxiety, fear, excitement, anger).
  • Activates reticular activating system (increases muscle tension and alertness).

Endocrine System

• Cortisol
  • Steroid hormone secreted by the adrenal cortex.
  • Released in response to ACTH from the anterior pituitary (stimulated by hypothalamus' CRH).
  • Functions:
    • Regulates blood glucose by converting fats/proteins to glucose.
    • Provides energy to muscles.
    • Has anti-inflammatory properties.
    • Suppresses immune system.
• Catecholamines (Epinephrine, Norepinephrine, Dopamine)
  • Secreted by chromaffin cells in the adrenal medulla.
  • Effects similar to the sympathetic nervous system.

General Adaptation Syndrome (GAS)

• Alarm Stage
  • Secretion of catecholamines and cortisol.
  • Activates sympathetic "fight or flight."
  • Suppression of thyroid, growth, and reproductive hormones (energy conservation).
  • Increased ADH secretion (fluid volume conservation and blood pressure maintenance).
• Resistance Stage
  • Cortisol levels decline (negative feedback).
  • Prolonged stress leads to harmful effects:
    • Immune system suppression.
    • Increased blood glucose and lipids.
    • Body tissue breakdown.
  • Long-term hormone suppression affects metabolism (e.g., hypertension).
• Exhaustion Stage
  • Degeneration of cells and tissues.
  • Significant health deterioration due to prolonged stress.

Conclusion

• Long-term stress adversely affects body organ systems.
• Understanding stress pathophysiology helps in recognizing its impact on health.