This nerve forms part of the eighth pair, and springs from the floor of the fourth ventricle above the nucleus of the vagus. It is a mixed nerve, the functions of which may be thus classified: -
Afferent fibres, which are of various kinds, viz.: -
(1) Sensory fibres, carrying impulses from the anterior surface of the epiglottis, the base of the tongue, the soft palate, the tonsils, the Eustachian tube and tympanum.
(2) Excito-motor - This nerve excites important reflex movements in swallowing and vomiting, when a stimulus is applied to the glosso-palatine arch.
(3) Excito-secretory, the stimulation of the back of the tongue gives rise to a copious flow of saliva by means of reflex action.
(4) Taste sensations are, for the most part, carried by this nerve; they are conveyed from special nerve endings in the back of the tongue (see Taste).
The efferent fibres are not so varied, being simply motor to the middle constrictor of the pharynx, stylo-pharyngeus, elevator of the soft palate, and the azygos uvulae.