Lecture Notes: Walter Cannon and the Stress Response

Introduction to Walter Cannon

• Who: American doctor in the early 1900s.
• Focus: Expanded understanding of homeostasis.
  • Homeostasis: Body's ability to maintain stable internal conditions (e.g., temperature, pH).
• Interest in Stress Response: Studied animals' homeostatic response to threats/dangers (stressors).
• Key Contribution: Coined the term "fight or flight response."

Fight or Flight Response

• Definition: Body prepares to fight or flee from stressors.
• Involvement:
  • Nervous System: Sympathetic nervous system activation.
    • Increased Heart Rate: Pumps blood with oxygen and nutrients.
    • Increased Respiratory Rate: More oxygen intake and carbon dioxide expulsion.
    • Peripheral Vasoconstriction: Blood vessels tighten to prioritize vital organs.
    • Suppression of Non-Essentials: Digestion, immune function, ovulation reduced.
  • Endocrine System: Hormonal support.
    • Adrenal Glands: Release catecholamines (epinephrine, norepinephrine) from the medulla.
    • Cortex Hormone: Cortisol from the cortex assists in stress response.

Tend and Befriend Response

• Definition: Response through huddling and forming support systems.
• Hormonal Influence:
  • Oxytocin: Associated with pair bonding.
  • Integration with Estrogen: Greater disposition in women.

General Adaptation Syndrome (GAS)

• Origin: Developed by Hans Selye, building on Cannon's research.
• Phases:
  • Alarm Phase: Stress reaction kicks in (heart racing, mobilized resources).
  • Resistance Phase: High temperature, blood pressure, and cortisol; body's reserves active.
  • Exhaustion Phase: Depletion of stress resources, tissue damage, and increased illness susceptibility.

Consequences of Chronic Stress

• Challenges: Body handles short-term stress well but struggles with long-term stress.
• Impact: Daily stressors can lead to exhaustion and negative health outcomes.