Figure 2.

Schematic representation of major developmental milestones in cough neurobiology. At birth, the airways are densely innervated by all nerve-fibre types. Laryngeal stimuli in the newborn predominately evokes the laryngeal chemoreflex, characterised by a cessation of breathing and swallowing. Apnoea is replaced by a cough later in postnatal development, but in prepubescent children the cough reflex has yet to fully mature, lacking the well-known sex differences in reflex sensitivity and an absence of cough hypersensitivity (CHS) as a major component of clinical cough in disease. By adulthood, females demonstrate a heighten reflex sensitivity compared to males and both females and males commonly display CHS in clinical conditions leading to an acute and chronic cough.