Dorsal motor nucleus of vagus and nucleus ambiguus (CN X)
Preganglionic · CN X Medulla
Medullary nuclei whose long preganglionic fibres run the length of the vagus: cardioinhibitory fibres arise mainly in nucleus ambiguus, secretomotor and visceromotor fibres to bronchi and gut in the dorsal motor nucleus. Fibres leave through the jugular foramen, descend in the carotid sheath, form the cardiac, pulmonary and oesophageal plexuses, and enter the abdomen as the anterior and posterior vagal trunks.
Traced from the start
- Parasympathetic (craniosacral) outflow
- Dorsal motor nucleus of vagus and nucleus ambiguus (CN X)
Detail
- Nucleus ambiguus
- Cardioinhibitory preganglionic neurones to SA and AV nodes (also branchiomotor to pharynx and larynx)
- Dorsal motor nucleus
- Secretomotor and motor to bronchi, oesophagus, stomach, small bowel and colon to the splenic flexure; parietal cell and pancreatic secretion
- Abdominal entry
- Oesophageal hiatus at T10 — anterior trunk mostly left vagus, posterior trunk mostly right ('LARP'); posterior trunk gives the coeliac branch
- Afferents
- About 80% of vagal fibres are afferent (baroreceptor, chemoreceptor, gut stretch) — the efferent limb is the minority
When it goes wrong
Pain, fear or prolonged standing triggers a Bezold–Jarisch type reflex with vagal surge and sympathetic withdrawal
Vasovagal syncope: prodromal nausea, sweating and pallor, then bradycardia with hypotension and brief loss of consciousness with rapid recovery lying flat
Lateral medullary (Wallenberg) infarction from PICA or vertebral occlusion involving nucleus ambiguus and descending sympathetic fibres
Ipsilateral palatal weakness, hoarseness and dysphagia with a central (first-order) Horner syndrome and crossed sensory loss
Practise this structure
1 question in the bank tagged Vagus Nerve.