The adrenal medulla is considered a modified sympathetic ganglion. Unlike typical postganglionic sympathetic neurons, the chromaffin cells of the medulla predominantly secrete:

• A Epinephrine (80%) and norepinephrine (20%) ✓
• B Norepinephrine (80%) and epinephrine (20%)
• C Dopamine as the primary catecholamine
• D Equal proportions of epinephrine and norepinephrine

Explanation

Unlike sympathetic nerve terminals (which release primarily norepinephrine), adrenal chromaffin cells express phenylethanolamine-N-methyltransferase (PNMT), which converts norepinephrine to epinephrine. Cortisol from the adjacent adrenal cortex diffuses into the medulla via the portal circulation and induces PNMT expression. Consequently, the human adrenal medulla secretes approximately 80% epinephrine and 20% norepinephrine. This ratio reverses in phaeochromocytoma or in extra-adrenal tumours (paragangliomas), which lack cortisol induction.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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