Vagus nerve
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The vagus nerve is tenth of twelve paired cranial nerves and is the only nerve that starts in the brainstem (somewhere in the medulla oblongata) and extends all the way down past the head, right down to the abdomen. The vagus nerve is arguably the single most important nerve in the body.
The medieval Latin word vagus means literally "wandering" (the words "vagrant", "vagabond", and "vague" come from the same root).
This nerve supplies motor and sensory parasympathetic fibres to pretty much everything from the neck down to the first third of the transverse colon. In this capacity, it is involved in, amongst other things, such varied tasks as heart rate, gastrointestinal peristalsis, sweating and speech (via the recurrent laryngeal nerve).
The vagus also controls a few skeletal muscles, namely:
- levator veli palatini muscle
- salpingopharyngeus muscle
- stylopharyngeus muscle
- palatoglossus muscle
- palatopharyngeus muscle
- superior, middle and inferior pharyngeal constrictors
- muscles of the larynx (speech).
This means that the vagus nerve is responsible for quite a few muscle movements in the mouth and also is vitally important for speech and in keeping the larynx open for breathing.
It also receives some sensation from the outer ear and part of the meninges.
Vagus nerve & the heart
Parasympathetic innervation of the heart is mediated by the vagus nerve. The right vagus innervates the SA node. Parasympathetic hyperstimulation predisposes those affected to bradyarrhythmias. The left vagus when hyperstimulated predisposes the heart to AV blocks.
External links
- Anatomy of the vagus (http://www.meddean.luc.edu/lumen/meded/grossanatomy/h_n/cn/cn1/cn10.htm) (Loyola medical school)
- Gray's Anatomy 1918 (http://www.bartleby.com/107/205.html)
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