The pharyngeal reflex or gag reflex is a reflex contraction of the back of the throat,1 evoked by touching the soft palate2, that prevents something from entering the throat except as part of normal swallowing. This helps prevent choking.
The afferent limb of the reflex is supplied by the glossopharyngeal nerve (cranial nerve IX), which inputs to the nucleus solitarius, and the efferent limb is supplied by the vagus nerve (cranial nerve X) from the nucleus ambiguus. Absence of the gag reflex 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, studies indicate that up to one-third of healthy people do not have a gag reflex.3
Swallowing unusually large objects or placing objects in the back of the mouth may cause pharyngeal reflex, and those who frequently experience the reflex will often train themselves to suppress it. In contrast, triggering the reflex is sometimes done intentionally to induce vomiting, for example by those who suffer from bulimia nervosa.
References
- ^ "Medical Neurosciences".
- ^ "pharyngeal reflex, gag reflex." WordNet 1.7.1. Princeton University, 2001. Answers.com 22 Apr. 2008. http://www.answers.com/topic/pharyngeal-reflex-gag-reflex
- ^ 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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