Which nerve fibers innervate eccrine sweat glands, and what neurotransmitter do they release?

Which nerve fibers innervate eccrine sweat glands, and what neurotransmitter do they release?

• A. Parasympathetic cholinergic fibers innervate eccrine glands and release acetylcholine.
• B. Sympathetic adrenergic fibers innervate eccrine glands and release norepinephrine.
• C. Sensory nerve fibers innervate eccrine glands to stimulate sweating.
• D. Sympathetic cholinergic nerve fibers innervate eccrine glands and release acetylcholine to stimulate sweating.

Answer: (D)

Eccrine sweat glands are controlled by sympathetic nerve fibers that release acetylcholine, not norepinephrine. This sympathetic cholinergic signaling stimulates sweating by acting on muscarinic receptors on the gland cells. The flow is: preganglionic sympathetic neurons release ACh onto nicotinic receptors of the postganglionic neuron, which then releases ACh onto muscarinic receptors of the eccrine gland to trigger secretion. This cholinergic sympathetic pathway is why sweating dissipates heat effectively, distinguishing eccrine control from the mostly adrenergic control of other sympathetic targets.

Eccrine sweat glands are controlled by sympathetic nerve fibers that release acetylcholine, not norepinephrine. This sympathetic cholinergic signaling stimulates sweating by acting on muscarinic receptors on the gland cells. The flow is: preganglionic sympathetic neurons release ACh onto nicotinic receptors of the postganglionic neuron, which then releases ACh onto muscarinic receptors of the eccrine gland to trigger secretion. This cholinergic sympathetic pathway is why sweating dissipates heat effectively, distinguishing eccrine control from the mostly adrenergic control of other sympathetic targets.