Hormonal Response to Stress: The Body's Defense Mechanism

Hormones coordinate the body's stress response. The hypothalamus activates the sympathetic nervous system (SNS) and hypothalamic-pituitary-adrenal (HPA) axis.

1. Sympathetic Nervous System Activation

• Hypothalamus stimulates SNS → adrenal medulla releases epinephrine (adrenaline).
• Epinephrine increases heart rate, blood pressure, respiration; dilates airways; redirects blood to brain/muscles ("fight or flight").

2. HPA Axis Activation

• Hypothalamus releases CRH → pituitary secretes ACTH.
• ACTH stimulates adrenal cortex → cortisol release (primary stress hormone).

3. Cortisol's Role

• Energy mobilization: Breaks down glycogen/fats → glucose/fatty acids for energy.
• Immunosuppression: Prevents excessive inflammation in acute stress.
• Metabolism regulation: Optimizes energy usage.
• Cognitive/emotional effects: Enhances focus, alertness.

4. Negative Feedback and Regulation

As stress resolves, hormone levels drop via negative feedback: reduced cortisol signals hypothalamus/pituitary to slow CRH/ACTH production, restoring baseline.

Essential for acute stress coping; chronic stress disrupts balance, potentially causing health problems if unmanaged.