Library · Physiology
The gag reflex
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The gag reflex, called the pharyngeal reflex in medicine, is the gagging that happens on its own when something touches the back of your throat. The pharynx, which is that back area, contracts all at once and the soft palate lifts. You do not decide it: it is a door that shuts on its own when something brushes it.
Among the spots that trigger it are the back wall of the pharynx, the area around the tonsils and the base of the tongue. That is why the doctor's tongue depressor and your toothbrush set it off so easily.
The circuit uses two different nerves, one going in and one coming back. The glossopharyngeal carries the sensation to the medulla oblongata, which is the lowest part of the brainstem, and the vagus sends back the command for the pharyngeal muscle to contract.
The response appears on both sides at once. The one on the side that was touched is called the direct reflex, and the one on the opposite side is the consensual reflex. And touch is not always necessary: for some people, just thinking they are about to be touched is enough, for example when they sit down in the dentist's chair.
In brief
The gag reflex, or pharyngeal reflex, is an involuntary pharyngeal contraction with elevation of the soft palate.
A door that shuts on its own when something brushes it.
Touching the posterior pharyngeal wall, the tonsils or the base of the tongue triggers it.
The glossopharyngeal nerve carries the signal to the medulla and the vagus sends the command back to the muscle.
The contraction happens on both sides: direct on the side touched, consensual on the other.
It can also fire without contact, from a mental stimulus alone.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Gag Reflex, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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