anatomy of sensory component

Last reviewed 01/2018

There are two functions of the sensory component of the facial nerve - both a general sensation of touch, pain and temperature, and the special sensation of taste.

Touch, pain and temperature stimuli are only gathered from a small region of skin on the ear. From here, neurones project centrally to the geniculate ganglion within the facial canal and thence to the spinal trigeminal nucleus within the pons. From here, neurones pass to the thalamus in the ventral trigeminothalamic tract.

Taste receptors from the palate synapse with processes of the palatine nerves to reach the geniculate ganglion by the following path: palatine nerve - nerve of pterygopalatine canal - greater petrosal nerve - geniculate ganglion.

Taste bud receptors from the anterior two thirds of the tongue pass sensory signals via the lingual nerve. This ascends through the middle ear cavity into the facial canal as the chorda tympani nerve, joining the facial nerve before heading onwards to the geniculate ganglion.

From the geniculate ganglion, the neuronal link from taste receptors passes centrally to the lower pons where it synapses with the nucleus tractus solitarius. Via the thalamus, this tract, which also has input from cranial nerves IX and X, finally projects to the postcentral gyrus of the sensory cortex.