Nucleus of solitary tract

Target:

• CN7 (SVA) ⇒ Taste from anterior 2/3 of tongue and palate

• CN9 (GVA) ⇒ Mucosa of tympanum , mastoid air cells, eustachian tube, tonsil, pharynx, soft palate

  • Carotid sinus baroreceptors

  • Carotid body chemoreceptors

• CN9 (SVA) ⇒ Taste, posterior 1/3 of tongue

• CN10 (GVA) ⇒ Visceral sensation from tonsils, larynx, thoracic and abdominal viscera, carotid sinus, carotid body

• CN10 (SVA) ⇒ Taste from epiglottis

Structure:

• Nuc. of solitary tract is an elongated column of cells and is intimately related to a group of descending fibres which constitute the tractus solitarius.

Location:

• The upper part of the nucleus lies deep in the reticular formation, ventrolateral to the dorsal nucleus of vagus.

• When traced downwards it lies in the dorsal part of central grey matter in the closed part of the medulla, dorsomedial to the dorsal nucleus of vagus.

• The lower ends of the nuclei of two sides fuse to form the commissural nucleus of the vagus.

• The rostral portion of the nuc. is concerned w/ taste sensations and receives the SVA fibres from facial, glossopharyngeal and vagus n. and is frequently referred to as gustatory nucleus.

• The nuclear terminations of VII, IX and X nerves are in rostrocaudal direction (Fig. 9.3). The caudal portion of the nucleus receives the general visceral sensations from pharynx (glossopharyngeal and vagus) and from oesophagus and abdominal part of alimentary canal up to right two-thirds of the transverse colon (vagus). It is presumed that axons from nucleus of tractus solitarius project to the thalamus and hypothalamus of the opposite side through the solitariothalamic and “solitariohypothalamic tracts respectively. These tracts join the medial lemniscus of the opposite side on their way to thalamus and hypothalamus. The neurons from thalamus then project to the cerebral cortex (Fig. 9.3).