Which statement correctly describes the innervation of eccrine sweat glands?

• A They are innervated by sympathetic adrenergic fibers releasing norepinephrine
• B They are innervated by sympathetic cholinergic fibers releasing acetylcholine ✓
• C They are innervated by parasympathetic cholinergic fibers releasing acetylcholine
• D They are innervated by somatic motor fibers releasing acetylcholine

Explanation

Eccrine sweat glands are innervated by postganglionic sympathetic cholinergic fibers that release acetylcholine onto muscarinic receptors. Although anatomically part of the sympathetic nervous system, these fibers use acetylcholine rather than norepinephrine, a classic exception. Parasympathetic fibers do not innervate sweat glands. Somatic motor fibers innervate skeletal muscle, not eccrine glands. This distinction is frequently tested in physiology examinations.

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

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