Stress and the Stress Response

Introduction

In this lecture, Doctor Deborah Coulson discusses the concept of stress and the body's stress response. The following notes outline the definitions, physiological mechanisms, and classifications of stress, as well as the implications of stress on health.

Stress Definition

Stress is defined as the body's psychological and physiological response to a perceived threat. This can include:

  1. Real Threats: An immediate danger, such as someone wielding a weapon.

  2. Implied Threats: Psychological responses to situations that may not present a direct physical threat but evoke feelings of fear based on past experiences. For example, seeing a dog running towards you may trigger stress based on a previous negative interaction with a dog.

The Stress Response

The stress response encompasses various physical and emotional changes in the body meant to regain homeostasis. Key components of the stress response include:

  1. Hormonal Changes:

    • Increased levels of adrenaline, noradrenaline, and cortisol.

  2. Homeostasis: The body’s effort to maintain equilibrium through continuous adjustment and compensation of physiological processes.

  3. Short-Term Responses: The initial, acute reactions intended to protect the body and manage stress (e.g. fight or flight responses).

  4. Long-Term Responses: Prolonged activation of the stress response which may lead to negative health outcomes.

Mechanisms of Stress Response

The body engages multiple systems to handle stress:

  1. Nervous System Activation: Involves the autonomic nervous system (ANS) and the sympathetic nervous system (SNS) which lead to:

    • Increased heart rate and blood pressure

    • Accelerated breathing rate

    • Dilation of pupils

    • Enhanced blood flow to muscles, heart, and lungs.

  2. Behavioral Responses: Individuals exhibit different coping mechanisms:

    • Some may eat or drink alcohol when stressed, others may exercise or isolate themselves.

Allostasis vs. Homeostasis

  1. Homeostasis entails maintaining a stable internal environment, whereas Allostasis is about achieving stability through change.

  2. Allostasis involves adaptations to acute stress, while long-term allostatic responses may lead to an allostatic load, where the body becomes overwhelmed and cannot effectively adapt to stressors.

Physiological Pathway of Stress Response

The stress response is also elucidated through the hypothalamic-pituitary-adrenal (HPA) axis:

  1. Stimulus Recognition: The brain recognizes a psychological or physiological threat.

  2. Hormonal Cascade:

    • Hypothalamus releases Corticotropin-Releasing Hormone (CRH).

    • Anterior pituitary gland is stimulated to release Adrenocorticotropic Hormone (ACTH).

    • ACTH drives the adrenal cortex to produce glucocorticoids, namely cortisol, which increases blood glucose levels for energy.

  3. Physical Responses: Simultaneous activation of the autonomic nervous system leads to rapid physiological changes to prepare for either fight or flight.

Hormonal Responses to Stress

  1. Adrenaline & Noradrenaline: Released almost instantaneously, vital for immediate fight or flight responses.

  2. Cortisol: Provides sustained energy supply and influences various processes, including metabolism, immune response, and other hormonal pathways.

  3. Other Hormones:

    • Prolactin: Suppresses reproductive functions during stress.

    • Endorphins: Mitigate pain perception.

    • Vasopressin: Helps retain fluids and regulate blood circulation under stress.

Types of Stressors

Stressors can be categorized into various types:

  1. Biological Stressors: Include infections, injuries, sleep disruptions, and heavy exercise.

  2. Chemical Stressors: Exposure to harmful chemicals, e.g., pesticides and fertilizers.

  3. Social Stressors: Issues like peer pressure, social isolation, or relationship breakdowns.

  4. Psychological Stressors: Emotional distress, anxiety, or pressures from academic assessments.

Individual Differences in Stress Perception

It is critical to note that individuals perceive stresses differently. A stimulus that is threatening for one person may not be perceived the same way by another, influenced by:

  1. Past Experiences: Historical interactions with certain stimuli (e.g., a past negative experience with dogs).

  2. Individual Psychology: Personal coping strategies and psychological resilience.

Conclusion

The stress response is a complex interplay of psychological and physiological factors. Understanding the stress mechanisms and acknowledging individual responses aid in comprehending its impact on health and well-being. Stress, while a natural reaction, prompts different coping strategies, and responses may vary extensively among individuals based on their unique histories and experiences.