Cough Reflex

Explain the pathways and importance of the cough reflex

Coughing:

  • Is an airway protection reflex
  • Involves deep inspiration followed by forced expiration against a closed glottis
    The sudden opening of the cords causes a violent rush of air at >900km.h-1, removing irritants and secretions from the airways.

Sensation

Vagus afferents have exquisitely sensitive light touch and corrosive chemical receptors in the larynx, carina, terminal bronchioles, and alveoli.

Integration

Vagal afferents synapse in the medulla, which coordinates the effector response.

Effector

A series of processes occur in three phases:

  • Inspiratory phase
    A close to vital capacity breath is taken.
  • Compressive phase
    Effort closure of the epiglottis to seal the larynx, followed by a violent contraction of abdominal musculature and internal intercostals, causing a rapid rise in intrapleural pressure to >100mmHg.
  • Expulsive phase
    Wide-opening of the cords and epiglottis, causing a violent expiration.
    • Compression of the lungs causes narrowing of the noncartilagenous airways and increases turbulent flow, removing adherent material from the tracheobronchial tree

References

  1. Barrett KE, Barman SM, Boitano S, Brooks HL. Ganong's Review of Medical Physiology. 24th Ed. McGraw Hill. 2012.
Last updated 2017-09-16

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