Lecture Notes: Walter Cannon and the Fight or Flight Response

Introduction to Walter Cannon

• Walter Cannon: American doctor in the early 1900s.
• Contributions: Expanded understanding of homeostasis - body's tendency to maintain internal stability despite external changes (e.g., temperature, pH).

Homeostatic Response to Stress

• Cannon focused on homeostatic responses to stressors (threats/dangers).
• Coined the term "fight or flight response":
  • Prepare to fight or run away from threats.
  • Involves the nervous system and endocrine system.

Nervous System

• Sympathetic Nervous System:
  • Part of the autonomic nervous system.
  • Activates the body’s "get out of danger" mode.
  • Effects include:
    • Increased heart rate (to pump oxygen and nutrients).
    • Increased respiration rate (more oxygen intake and CO2 expulsion).
    • Peripheral vasoconstriction: Blood vessels in limbs constrict to direct blood to vital organs.
    • Suppression of non-essential functions (digestion, immune function, ovulation).

Endocrine System

• Adrenal Glands:
  • Located above the kidneys.
  • Adrenal Medulla: Releases catecholamines (epinephrine/adrenaline, norepinephrine/noradrenaline).
    • Increases heart rate and blood pressure.
  • Adrenal Cortex: Releases cortisol (a glucocorticoid).
    • Redistributes glucose, suppresses immune system.

Additional Stress Responses

• Tend and Befriend Response:
  • Sometimes, social connection is a better stress response.
  • Involves hormone oxytocin (related to pair bonding).
  • More prevalent in women due to estrogen relationship.

General Adaptation Syndrome (GAS)

• Developed by Hans Selye in the 20th century.
• Stages of Stress Response:
  1. Alarm Phase: Initial stress reaction (heart racing, resource mobilization).
  2. Resistance Phase: Continued fight or flight response, high cortisol levels.
  3. Exhaustion Phase: Depletion of resources leads to tissue damage, weakened immunity.

Implications of Chronic Stress

• Chronic Stress: Long-term exposure to stress exhausts resources.
• Leads to negative health consequences due to overexposure (e.g., susceptibility to illness).
• Importance of understanding and managing stress in daily life.