Postganglionic sympathetic fibres supplying eccrine sweat glands are unusual among sympathetic postganglionic fibres because they:

• A Release norepinephrine acting on beta-2 receptors
• B Release acetylcholine acting on muscarinic receptors ✓
• C Synapse in the adrenal medulla before reaching the gland
• D Pass through the sympathetic chain without synapsing

Explanation

Eccrine sweat glands are the classic exception to the rule that sympathetic postganglionic neurons are adrenergic: their postganglionic fibres release acetylcholine, which acts on muscarinic receptors. This explains why anticholinergic drugs cause anhidrosis and why sweating accompanies cholinergic crises such as organophosphate poisoning. Apocrine sweat glands, by contrast, are adrenergically innervated. Options C and D describe preganglionic pathways to the adrenal medulla and to prevertebral ganglia respectively, not postganglionic supply to skin.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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