Testing of the gag reflex involves which two cranial nerves as afferent and efferent limbs respectively?

• A CN V (afferent from soft palate) and CN X (efferent to pharyngeal constrictors)
• B CN IX (afferent from posterior pharyngeal wall) and CN X (efferent to pharyngeal muscles) ✓
• C CN VII (afferent from anterior two-thirds of tongue) and CN XII (efferent to tongue)
• D CN X (afferent and efferent via recurrent laryngeal branch)

Explanation

The gag reflex afferent limb is carried by CN IX (glossopharyngeal nerve), which provides general somatic afferent fibers from the posterior pharyngeal wall and the posterior one-third of the tongue. The efferent limb is CN X (vagus nerve), which innervates the pharyngeal constrictor muscles (through the pharyngeal plexus) causing elevation of the palate and pharyngeal contraction. The reflex arc: touch posterior pharyngeal wall → CN IX → nucleus ambiguus → CN X → pharyngeal muscles contract. Absence may indicate CN IX, X lesions or brainstem pathology.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.