Category: signaling
The cough reflex protects the airway. AFFERENT limb: irritants, mucus, or inflammation activate vagal sensory afferents — C-fibers (via TRPV1/TRPA1) and rapidly-adapting receptors — which relay through the nucleus tractus solitarius to a medullary cough-generating network. EFFERENT limb: the cough center drives a coordinated deep inspiration, glottic closure, and forced expiration. Central antitussives suppress the brainstem cough network: dextromethorphan (sigma-1 / NMDA modulator, non-opioid) and codeine (μ-opioid agonist; also a morphine prodrug). Peripheral protussives/mucolytics act on the airway side instead. Cross-link: mu_opioid.