Cough reflex

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The cough reflex has both sensory (afferent) and motor (efferent) pathways. The internal laryngeal nerve carries the sensory information away from the area above the glottis in the trachea to the CNS via cranial nerve X (vagus). Stimulation of this area by foreign particles produces powerful cough.

A cough consists of a number of physiological steps:

1. Rapid inspiration of approximately 2.5 litres of air.
2. The epiglottis and the vocal cords close to trap air in the lungs.
3. The muscles used for expiration forcefully contract, raising the air pressure in the lungs.
4. The epiglottis and the vocal chords open suddenly, allowing air to rush out.