Nucleus of tractus solitarius

The nucleus of tractus solitarius is a brainstem nucleus on each side of the upper medulla. It lies lateral to the dorsal nucleus of the vagus, to which it has many connecting neurones, and medial to the spinal tract and the nucleus of the trigeminal nerve. The nucleus has afferent fibres which extend inferiorly within the upper medulla as the tract of solitarius.

The superior part of the nucleus receives fibres from the:

• chorda tympani branch of the facial nerve; involved with taste sensation from the anterior two thirds of the tongue
• lingual branch of the glossopharyngeal nerve; involved with taste from the posterior third of the tongue
• internal laryngeal branch of vagus nerve; involved with taste in the region of the valleculae; possibly some taste fibres from region of the epiglottis

The inferior part of the nucleus receives fibres from the:

• vagus nerve:
  • visceral afferent fibres from heart
  • widespread general visceral sensory from the abdominal viscera to the junction of midgut and hindgut
• glossopharyngeal nerve: special visceral sensory from the arterial receptors in the carotid body and sinus

The nucleus of tractus solitarius is connected to the:

• dorsal nucleus of the vagus
• reticular formation

Functionally, cells of the nucleus play a role in the:

• blood pressure regulation
• cough reflex
• gag reflex
• sneeze reflex
• vomiting
• inspiration