Which nerve stimulates tear production?

• A. Lacrimal nerve
• B. Greater petrosal (CN VII)
• C. Deep petrosal
• D. Vidian nerve

Answer: (B)

Tear production is driven by parasympathetic secretomotor fibers. The pathway begins with the greater petrosal nerve, a branch of the facial nerve, carrying preganglionic parasympathetic fibers from the superior salivatory nucleus. These fibers join with deep petrosal fibers to form the nerve of the pterygoid canal (Vidian nerve) and travel to the pterygopalatine ganglion. From there, postganglionic fibers hitchhike with branches of the maxillary and lacrimal nerves to reach the lacrimal gland and stimulate secretion. The greater petrosal nerve is the key conduit for the parasympathetic input that triggers tearing. Deep petrosal carries sympathetic fibers (not tear production), and while the Vidian nerve is the composite trunk to the ganglion, the initiating parasympathetic path originates with the greater petrosal nerve.