Pharyngeal reflex

The pharyngeal reflex or gag reflex is a reflex muscular contraction of the back of the throat, evoked by touching the roof of the mouth, back of the tongue, area around the tonsils, uvula, and back of the throat. It, along with other aerodigestive reflexes such as reflexive pharyngeal swallowing, prevents objects in the oral cavity from entering the throat except as part of normal swallowing and helps prevent choking, and is a form of coughing. The pharyngeal reflex is different from the laryngeal spasm, which is a reflex muscular contraction of the vocal cords.

In a reflex arc, a series of physiological steps occur very rapidly to produce a reflex. Generally, a sensory receptor receives an environmental stimulus, in this case from objects reaching nerves in the back of the throat, and sends a message via an afferent nerve to the central nervous system (CNS). The CNS receives this message and sends an appropriate response via an efferent nerve (also known as a motor neuron) to effector cells located in the same initial area that can then carry out the appropriate response.

In the case of the pharyngeal reflex:

The gag reflex involves a brisk and brief elevation of the soft palate and bilateral contraction of pharyngeal muscles evoked by touching the posterior pharyngeal wall. Touching the soft palate can lead to a similar reflex response. However, in that case, the sensory limb of the reflex is the CN V (trigeminal nerve). In very sensitive individuals, much more of the brain stem may be involved; a simple gag may enlarge to retching and vomiting in some.

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, by those who have bulimia nervosa.

According to one study, one in three people lacks a gag reflex. However, on the other end of the spectrum are people with a hypersensitive gag reflex. This hypersensitivity can lead to issues in various situations, such as swallowing a pill or large bites of food, or visiting the dentist. Hypersensitivity is generally a conditioned response, usually occurring following a previous experience. There are a variety of ways to desensitize one's hypersensitivity, from relaxation to numbing the mouth and throat to training one's soft palate to get used to being touched.^{[citation needed]}

Anti-nausea medicines, sedatives, local and general anaesthetics, herbal remedies, behavioural therapies, acupressure, acupuncture, laser, and prosthetic devices can be used to manage exaggerated gag reflex during dental treatment. Studies showed with very low‐certainty evidence that acupuncture and laser at the P6 point (located in the wrist) reduced gagging without sedation. However, there was no difference when practiced with sedation. Therefore, more research needs to be carried out regarding these interventions.

Some people seem to be able to completely stop their gag reflex for a short time by pressing certain pressure points, even without prior training.