It serves to clear the airway of excessive secretions and foreign matter. It can be either voluntary or involuntary. Cough receptors are located within the epithelial layer of respiratory tissue. There are both mechanical receptors and chemical receptors. The mechanical receptors are sensitive to touch and displacement and are located primarily in the larynx, trachea, and carina.
Chemical receptors are sensitive mostly to noxious gases and fumes.
These receptors are located more in the larynx and bronchi. Receptors are found in respiratory bronchioles. but extend no further down the respiratory tree then this. Cough receptors tend to become less sensitive when continuously stimulated. Cough receptors send their impulses to a central cough center via the vagus nerve, the glossophayrngeal, trigeminal and phrenic nerves. The vagus may also send messages to the cough center from higher centers of the brain.