Eccrine sweat glands produce sweat in response to thermal stress. What is their autonomic innervation?

• A Sympathetic cholinergic fibers releasing acetylcholine ✓
• B Sympathetic adrenergic fibers releasing norepinephrine
• C Parasympathetic cholinergic fibers releasing acetylcholine
• D Sympathetic fibers co-releasing norepinephrine and dopamine

Explanation

Eccrine sweat glands are innervated by sympathetic postganglionic fibers that release acetylcholine acting on muscarinic receptors, an exception to the usual adrenergic sympathetic transmission. Anticholinergic drugs therefore reduce sweating and predispose to hyperthermia. Apocrine glands respond to adrenergic stimulation, and no parasympathetic supply reaches the skin sweat glands.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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