The pharyngeal reflex or gag reflex is a reflex contraction of the back of the throat,[1] evoked by touching the soft palate or sometimes the back of the tongue. It prevents something from entering the throat except as part of normal swallowing and helps prevent choking. Different people have different sensitivities to the gag reflex.
The afferent limb of the reflex is supplied by the glossopharyngeal nerve (cranial nerve IX), which inputs to the nucleus solitarius and the spinal trigeminal nucleus, and the efferent limb is supplied by the vagus nerve (cranial nerve X) from the nucleus ambiguus. Absence of the gag reflex and pharyngeal sensation can be a symptom of a number of severe medical conditions, such as damage to the glossopharyngeal nerve, the vagus nerve, or brain death. However, in one study, one-third of healthy people did not have a gag reflex, although pharyngeal sensation in these subjects remained intact.[2]
Swallowing unusually large objects or placing objects in the back of the mouth may cause the pharyngeal reflex. Some people, for instance sword swallowers, have learned how to suppress it. In contrast, triggering the reflex is sometimes done intentionally to induce vomiting, for example by those who suffer from bulimia nervosa.
[edit] References
- ^ "Medical Neurosciences". http://www.neuroanatomy.wisc.edu/virtualbrain/BrainStem/09NA.html.
- ^ Pharyngeal sensation and gag reflex in healthy subjects. Davies, A., Kidd, D., Stone, S., MacMahon, J. (1995). Lancet 345:487–488
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