Posterior nucleus of vagus nerve

At a glance

English

Posterior nucleus of vagus nerve

Latin (TA2)

Nucleus posterior nervi vagi

System

Nerve

Region

Head

Side

Paired, left and right

About the posterior nucleus of vagus nerve

The posterior (dorsal) nucleus of the vagus nerve, also called the dorsal vagal nucleus, is the largest parasympathetic nucleus of the brainstem. Its preganglionic neurons send fibres out in the vagus nerve to the organs of the chest and abdomen, above all the digestive tract from the oesophagus to roughly the left colic flexure, and to the airways.

It is a long column of cells in the medulla, starting near the lower limit of the fourth ventricle and extending into the closed medulla beside the central canal. In the open medulla it lies just beneath the ventricular floor, under the vagal triangle (trigone), with the hypoglossal nucleus immediately medial to it and the solitary nucleus just lateral and in front. Its axons run forwards and outwards through the medulla and leave with the other vagal fibres as rootlets in the groove behind the olive.

Its fibres end on small ganglia in or near the walls of the organs they serve, from which short postganglionic fibres reach smooth muscle and glands. Through them the nucleus increases gut movement and secretion, relaxes sphincters, constricts the bronchi and boosts their gland output. Most of the vagal fibres that slow the heart begin not here but in a nearby group around the nucleus ambiguus, a separate column that also supplies the striated muscles of the pharynx, larynx and the uvula.

The nucleus works closely with its sensory neighbour. Signals from the stomach, intestine and lungs travel up the vagus to the solitary nucleus, which projects to the dorsal vagal nucleus and adjusts its output. These short loops, called vagovagal reflexes, control such things as the stomach relaxing to receive a meal and the release of digestive juices. The nucleus also takes in signals from the hypothalamus, so emotion and stress can change gut activity. In Parkinson's disease it is one of the first brainstem regions affected, which may underlie the constipation that often appears early in the illness.

Course and supply

Supplies

Sends preganglionic parasympathetic fibres in the vagus to the thoracic and abdominal organs, promoting gut motility and secretion and causing bronchoconstriction and bronchial gland secretion.

Blood supply

Branches of the vertebral and posterior inferior cerebellar arteries supplying the dorsal medulla.