BP103T • Unit 4Topic 1 of 3⏱ 5 Min Read

1. Psychophysiology of Stress & Selye's General Adaptation Syndrome (GAS)

💡 Core Concept & Clinical Context:

Stress is the non-specific physiological and psychological response of the body to any demand or noxious stressor. Endocrinologist Hans Selye formulated the General Adaptation Syndrome (GAS) model, detailing how chronic exposure to physiological or psychological stressors activates the Sympathetic-Adrenomedullary (SAM) axis (releasing Epinephrine and Norepinephrine) and the Hypothalamic-Pituitary-Adrenal (HPA) axis (releasing Corticotropin-Releasing Hormone, ACTH, and Cortisol). The GAS model comprises three distinct physiological stages: (1) Alarm Reaction, (2) Stage of Resistance, and (3) Stage of Exhaustion.

Clinical Scenarios & Pharmacopoeial Examples:

1The Three Stages of Hans Selye's GAS Model

Physiological shifts during acute vs prolonged chronic stress.

Step-by-Step Breakdown:

•1. Stage 1: Alarm Reaction:

•• Immediate 'Fight-or-Flight' response activated by sympathetic nervous system.

•• Physiological Changes: Surge in Epinephrine and Norepinephrine; tachycardia, bronchodilation, glycogenolysis, pupil dilation, redirected blood flow to skeletal muscles.

•2. Stage 2: Stage of Resistance (Adaptation):

•• The body attempts to adapt and maintain homeostatic equilibrium against persistent stressor.

•• Physiological Changes: HPA axis sustains elevated systemic Cortisol levels; blood glucose remains elevated; immune and reproductive functions are suppressed.

•3. Stage 3: Stage of Exhaustion:

•• Prolonged, unmitigated stress depletes adaptive physiological reserves.

•• Clinical Consequences: Severe immunosuppression, clinical hypertension, peptic ulceration, chronic fatigue, depressive illness, cardiovascular disease.

📋Key Takeaways & Exam Highlights

Eustress: Positive, adaptive, motivating stress that enhances performance (e.g. studying for examinations).
Distress: Negative, debilitating, unmanageable stress that impairs physiological function and mental health.
Allostatic Load: The cumulative physiological wear and tear on tissues and organs resulting from chronic stress exposure.
HPA Axis: Hypothalamus $\rightarrow$ CRH $\rightarrow$ Anterior Pituitary $\rightarrow$ ACTH $\rightarrow$ Adrenal Cortex $\rightarrow$ Cortisol.

🇮🇳 हिन्दी व्याख्या (1. Psychophysiology of Stress & Selye's General Adaptation Syndrome (GAS))

हंस सेली का GAS मॉडल बताता है कि तनाव के 3 चरण होते हैं: (1) अलार्म रिएक्शन (तुरंत लड़ो या भागो प्रतिक्रिया), (2) प्रतिरोध (शरीर कोर्टिसोल बढ़ाकर संतुलन बनाने की कोशिश करता है), और (3) थकावट (शरीर की क्षमता समाप्त होकर बीमारियां घेर लेती हैं)।