The function of both the cough reflex and the sneeze reflex is to dislodge foreign matter or irritating material from respiratory passages. The bronchi and the trachea contain sensory receptors that are sensitive to foreign particles and irritating substances. The cough reflex is initiated with the sensory receptors detect these substances and initiate action potentials that pass along the vagus nerves to the medulla oblongata, where the cough reflex is triggered.

The movements resulting in a cough occur as follows: about 2.5 litters (L) of air are inspired, the epiglottis closes, and the vestibular folds and vocal cords close tightly to trap the inspired air in the lung; the abdominal muscles contract to force the abdominal contents up against the diaphragm; and the muscles of expiration contract forcefully. As a consequence, the pressure in the lungs increase to about 100 mm Hg. Then the vestibular folds, the vocal cords, and the epiglottis open suddenly, and the air rushes from the lungs at a high velocity, carrying foreign particles with it.

The sneeze reflex is similar to the cough reflex, but it differs in several ways. The source of irritation that initiates the sneeze reflex is in the nasal passages instead of in the trachea and bronchi, and the action potentials are conducted along the trigeminal nerves to the medulla, where the reflex is triggered. During the sneeze reflex the uvula and the soft palate are depressed so the air is directed primarily through the nasal passages, although a considerable amount passes through the oral cavity. The rapidly flowing air dislodges particulate matter from the nasal passages and propels it a considerable distance from the nose.

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