Question
Compare the adrenal cortex and adrenal medulla in terms of structure, hormones produced, and functions. Why is adrenaline called the “emergency hormone”? What are the three zones of the adrenal cortex and their hormones?
(NEET + CBSE Board pattern)
Solution — Step by Step
| Feature | Adrenal Cortex (outer) | Adrenal Medulla (inner) |
|---|---|---|
| Origin | Mesoderm | Neural crest (ectoderm) |
| Type of hormones | Steroid hormones (from cholesterol) | Catecholamines (amino acid derivatives) |
| Regulation | ACTH from pituitary | Sympathetic nervous system |
| Response speed | Slow (hours) | Fast (seconds) |
| Key hormones | Cortisol, aldosterone, androgens | Adrenaline (epinephrine), noradrenaline |
| Zone | Hormone | Function |
|---|---|---|
| Zona glomerulosa (outermost) | Aldosterone (mineralocorticoid) | Regulates Na⁺/K⁺ balance, blood pressure |
| Zona fasciculata (middle, largest) | Cortisol (glucocorticoid) | Increases blood glucose, anti-inflammatory, stress response |
| Zona reticularis (innermost) | Androgens (DHEA) | Secondary sexual characters, supplementary sex hormones |
Memory aid: GFR — Glomerulosa, Fasciculata, Reticularis (from outside to inside). The hormones follow alphabetical order too: Aldosterone, Cortisol, DHEA.
When you face a threat (tiger, exam paper, car accident), the sympathetic nervous system fires and stimulates the adrenal medulla to release adrenaline within seconds. The effects:
- Heart rate increases (more blood to muscles)
- Pupils dilate (better vision)
- Airways dilate (more oxygen)
- Blood glucose rises (energy for muscles)
- Blood is diverted from gut to skeletal muscles
- Sweating increases (cooling)
This is the fight-or-flight response — the body prepares to either confront or escape the danger. All of this happens in seconds, which is why the adrenal medulla is under nervous control (not hormonal) — the nervous system is faster than the endocrine system.
graph TD
A["Adrenal Gland"] --> B["Cortex - outer"]
A --> C["Medulla - inner"]
B --> B1["Zona Glomerulosa → Aldosterone"]
B --> B2["Zona Fasciculata → Cortisol"]
B --> B3["Zona Reticularis → Androgens"]
C --> C1["Adrenaline"]
C --> C2["Noradrenaline"]
C1 --> D["Fight-or-Flight Response"]
B2 --> E["Stress Adaptation"]
style A fill:#fbbf24,stroke:#000,stroke-width:2px
style D fill:#fca5a5,stroke:#000,stroke-width:2pxWhy This Works
The adrenal gland is essentially two glands in one. The cortex produces steroid hormones for long-term regulation (fluid balance, metabolism, stress adaptation). The medulla produces catecholamines for immediate emergency responses. This dual nature reflects their different embryonic origins — the cortex from mesoderm, the medulla from neural crest ectoderm.
Cortisol is sometimes called the “stress hormone” — it helps the body cope with prolonged stress by maintaining blood glucose levels and suppressing non-essential functions like immune response and digestion.
Common Mistake
Students often confuse aldosterone (mineralocorticoid, from zona glomerulosa) with cortisol (glucocorticoid, from zona fasciculata). Remember: Aldosterone regulates aldosterone — no, better: Aldosterone deals with minerals (Na⁺, K⁺). Cortisol deals with glucose (glucocorticoid). Also, Addison’s disease is hypo-adrenal (low cortisol/aldosterone); Cushing’s syndrome is hyper-adrenal (excess cortisol).
NEET loves the mnemonic for adrenal cortex zones: GFR makes Salt, Sugar, Sex — Glomerulosa makes mineralocorticoids (salt balance), Fasciculata makes glucocorticoids (sugar), Reticularis makes androgens (sex hormones). This single mnemonic covers the entire cortex.