The cough reflex is a coordinated neural and muscular response to the irritation of the respiratory system. As a reflex action, coughing does not require conscious direction or control. Coughing is a nociceptive reflex, designed to protect the body from injury.

Coughing is initiated by the sensory neurons lining the respiratory passages. Afferent neural impulses produced in respiratory structures travel via the vagal nerve to the medulla of the brain and result in the appropriate muscular excitations to produce an acute expulsion of air designed to clear the respiratory passages. Irritation of the respiratory passages may result from contact with a foreign body, mechanical obstruction of the airway, or by an excessive buildup of fluid that obstructs a portion of an airway.

The coordinate cough reflex involves the inspiration of air and the subsequent closure of the epiglottis and the vocal cords that traps the air...