Secretomotor

Secretomotor refers to the functional class of autonomic nerve fibers that stimulate secretion from exocrine glands. In humans, secretomotor neurons are part of the autonomic nervous system; preganglionic neurons originate in the brainstem and synapse in specific ganglia, with postganglionic fibers delivering signals to glands to increase or modulate secretion.

The major secretomotor pathways for salivary and lacrimal glands involve parasympathetic transmission using acetylcholine and muscarinic receptors. Salivary secretion to the submandibular and sublingual glands is carried by postganglionic fibers that originate from the chorda tympani (branch of cranial nerve VII) joining the lingual nerve to reach the submandibular ganglion; postganglionic fibers supply the submandibular and sublingual glands. Parotid gland innervation comes from the glossopharyngeal nerve IX via the otic ganglion and auriculotemporal nerve. Lacrimal gland and nasal mucosa receive secretomotor input from the greater petrosal nerve (branch of VII) to the pterygopalatine ganglion, with postganglionic fibers reaching lacrimal glands and nasal mucosa.

Sympathetic secretomotor pathways also exist, notably to sweat glands, where postganglionic sympathetic fibers release acetylcholine to muscarinic receptors; most other secretory responses in glands are parasympathetic. Co-transmitters such as vasoactive intestinal peptide (VIP) may augment secretion in some contexts.

Clinical relevance: Disruption of secretomotor pathways can lead to conditions such as xerostomia (dry mouth), impaired lacrimation, or abnormal sweating. Lesions of cranial nerves VII or IX, autonomic neuropathies, or autoimmune diseases affecting secretory glands can alter secretomotor function.