Cranial Nerve X: Vagus Nerve

Organ system: The cranial nerves

Structure

• The vagus nerve has a very long path through the body, reaching as far as the transverse colon.

 

Functions

Autonomic

• Carries parasympathetic signals between the CNS and most of the body. At the level of the pelvis, parasympathetic functions are mediated by the pelvic splanchnic nerves instead.
• In particular, the vagus nerve promotes gastrointestinal activity. 
• As vagal tone increases, the heart rate and stroke volume decrease.

Motor

• Motor output to the palatoglossus muscles.
• Motor output during swallowing (alongside CN-IX and CN-XII).
• Motor output during the pharyngeal (gag) reflex.

 

Pathology

• Peptic ulcer disease: The vagus nerve stimulates gastrointestinal acid secretion, and therefore contributes to gastrointestinal ulceration.
• Autonomic dysfunction in spinal cord injury: The sympathetic nervous system transmits signals through the spinal nerves and therefore cannot function after a severe spinal cord injury. The vagus nerve leaves the brain, not the spinal cord, and continues to function despite any spinal cord injuries. This leaves the parasympathetic output is unopposed and can cause life-threatening hypotension.
• Vagotomy: Surgical or traumatic removal of the vagus nerve reduces parasympathetic output to most of the body.