However, a suction device may be most convenient for testing in an intubated patient. The gag reflex can be elicited using a tongue blade or soft cotton applicator. Here, sensory stimulation of the soft palate travels through the nucleus of the spinal tract of the trigeminal nerve. Stimulation of the soft palate can also elicit the gag reflex in this case, the sensory limb is the trigeminal nerve (CN V). Efferent nerve fibers to the pharyngeal musculature traverse from the nucleus ambiguus through CN X, resulting in the bilateral contraction of the posterior pharyngeal muscles.Ĭontraction of the pharyngeal musculature ipsilateral to the side of the stimulus is known as the direct gag reflex, and contraction of the musculature on the contralateral side is known as the consensual gag reflex. In turn, these nuclei send fibers to the nucleus ambiguus, a motor nucleus in the rostral medulla. These sensations are carried by CN IX, which acts as the afferent limb of the reflex to the ipsilateral nucleus solitarius (also referred to as the gustatory nucleus) after synapsing at the superior ganglion located in the jugular foramen. The stimulus is provided by sensation to the posterior pharyngeal wall, the tonsillar pillars, or the base of the tongue. The nerve roots of cranial nerves IX and X exit the medulla through the jugular foramen and descend on either side of the pharynx to innervate the posterior pharynx, posterior one-third of the tongue, soft palate, and the stylopharyngeus muscle. The gag reflex is controlled by both the glossopharyngeal (CN IX) and vagus (CN X) nerves, which serve as the afferent (sensory) and the efferent (motor) limbs for the reflex arc, respectively. In cases of psychogenic gag reflexes, even the thought of touching a sensitive trigger area, such as occurs when going to the dentist, can induce gagging. A psychogenic gag reflex presents following a mental trigger, typically without direct physical contact. A somatogenic gag reflex follows direct physical contact with a trigger area, which may include the base of the tongue, posterior pharyngeal wall, or tonsillar area. The gag reflex can be classified as either somatogenic or psychogenic. Starting around six or seven months of age, the gag reflex diminishes, allowing infants to swallow more solid foods. In the first few months of life, the gag reflex is triggered by any food that the nucleus tractus solitarius (a region of the brain stem) deems too large or solid for a baby to digest. The gag reflex is a natural somatic response in which the body attempts to eliminate unwanted agents or foreign objects from the oral cavity through muscle contraction at the base of the tongue and the pharyngeal wall. Embryologically, the glossopharyngeal nerve is associated with the derivatives of the third pharyngeal arch, while the vagus nerve is associated with the derivatives of the fourth and sixth pharyngeal arches. The gag reflex is mediated by the glossopharyngeal nerve (CN IX) and the vagus nerve (CN X).

Contrast this with a hypersensitive gag reflex (HGR), which may be caused by anxiety, postnatal drip, acid reflux, or oral stimulation, such as during dental treatments.

In certain instances, a lack of a gag reflex may be a symptom of a more severe medical condition, such as cranial nerve damage or brain death. It is an essential component of evaluating the medullary brainstem and plays a role in the declaration of brain death. The gag reflex is believed to be an evolutionary reflex that developed as a method to prevent swallowing foreign objects and prevent choking. The gag reflex, also known as the pharyngeal reflex, is an involuntary reflex involving bilateral pharyngeal muscle contraction and elevation of the soft palate. This reflex may be evoked by stimulation of the posterior pharyngeal wall, tonsillar area, or base of the tongue.

No gag reflexes