Gag Reflex: Function, Tasks, Role & Diseases

The gag reflex is a protective reflex designed to prevent foreign bodies or liquids from accidentally entering the airway, swallowing objects that are too large, or swallowing food that is extremely bitter, for example. The reflex is triggered by touching the base of the tongue and/or the soft palate, especially the palatal arches. The gag reflex is executed by a contraction of the muscles of the posterior pharynx.

What is the gag reflex?

The gag reflex is a protective reflex designed to prevent foreign bodies or liquids, for example, from accidentally entering the airway. The gag or choke reflex is used to protect the respiratory tract and the gastric tract from accidental entry of foreign bodies. In the case of the trachea, the reflex prevents the entry of a solid body. In the case of the esophagus, the purpose is to prevent accidental swallowing of an object that is too large or very bitter or spoiled food that might indicate poison. The gag reflex is placed in the category of extraneous or multisynaptic reflexes because the trigger of the reflex is not also the effector. The reflex is triggered by touching the base of the tongue and/or the soft palate (soft palate), but not by touching the uvula. The execution, on the other hand, is accomplished by the muscles of the posterior pharynx. The vagus nerve and the glossopharyngeal nerve are involved in the execution and coordination of the reflex. The glossopharyngeal nerve is also known as the 9th cranial nerve, which carries mainly visceromotor and viscerosensory fibers in addition to somatosensory nerve fibers. The vagus nerve is the 10th cranial nerve and is also composed of mixed somatosensitive, viscerosensitive, and -motor fibers.

Function and task

One of the primary functions and tasks of the gag reflex is to protect the trachea from foreign bodies or from obstruction and thus from suffocation. Simultaneous protection against accidental swallowing of large objects and spoiled or very bitter food that might be toxic is also one of the primary tasks of the reflex. The reflex is usually so strong that it functions even in unconsciousness and is even used as one of several tests to determine brain death. In addition to the gag reflex being triggered by mechanical-physical touch stimuli of the soft palate or base of the tongue, the reflex can also be mentally generated by feelings of disgust. In contrast to the innate “mechanical” trigger of the reflex, disgust is acquired through experience and imagination. Traditional food prohibitions or repeated negative experiences of eating certain foods can cause a strong aversion to the point of producing the gag reflex with vomiting. If the sight of certain food triggers a feeling of disgust, the sense of taste can also trigger the gag reflex if the “disgusting'” food accidentally enters the mouth and only the taste buds notice this. Phobias, such as a spider phobia, which is actually triggered by fear, can also cause a gag reflex. In a broader sense, therefore, the reflex serves not only to provide immediate protection from choking and to protect the esophageal and gastric tracts from mechanical danger and from possible poisoning, but also to avoid certain foods that are socially taboo. Thus, the gag reflex also has an important social component.

Diseases and ailments

The most common problem associated with the gag reflex is oversensitization. It manifests itself during upcoming examinations of the mouth and throat or during dental treatments during which the gag reflex occurs and is unpleasant and disturbing for both sides, patient and doctor. The oversensitization of the reflex can be so strong that even the sight of the instrument that has to be inserted into the oral cavity can trigger a nausea. Other disturbance of the gag reflex may have a variety of causes. Purely anatomical changes in the pharynx may be the culprit for a malfunction of the reflex or neuronal problems affecting the 9th and 10th cranial nerves. Neuronal problems can occur, for example, because of an accident with lesion of the 9th or 10th cranial nerve, because of a stroke, or because of a nerve disease. The glossopharyngeal nerve, which is involved in the gag reflex, can cause a so-called glossopharyngeal spasm.This is a spasm of the pharyngeal muscles, which are also responsible for the gag reflex. Such a spasm can be triggered by a rabies] or tetanus infection, whereby tetanus and botulinum toxins can completely paralyze the nerve. A third complex of causes for a disorder of the gag reflex lies in psychological disorders that can lead to oversensitization. In this context, a classic conditioning of the reflex in a dental practice can occur when, for example, a somewhat insensitive handling of an impression tray with too much impression material triggered a strong gag reflex in a patient, which the patient was no longer able to suppress. In appropriately sensitive patients, this may be sufficient for conditioning, i.e., reinforcement of the reflex. Frequent passive or active triggering of the reflex can lead to desensitization to the point of complete cessation. A classic example is people suffering from bulimia who frequently use the gag reflex to vomit. Targeted desensitization on a psychological basis under the guidance of a therapist to return the gag reflex to a “normal level” can be useful. If successful, this will prevent any dental treatment or any treatment involving the mouth and throat from becoming a problem case with the need for sedation with a sedative or even the need for a short anesthetic. Targeted acupuncture treatment can also be used successfully for desensitization.