Cough reflex (mechanism of cough)

Cough is a protective mechanism to protect the airways from harmful irritants. The reflex arc in a cough reflex include the following components:

  • Cough receptors:
    • They are located in different parts of the respiratory system, diaphragm and even in certain areas of the gastrointestinal system
    • When they are exposed to irritating substances, they are stimulated
  • Afferent pathway
    • Impulses are transmitted along the glossopharyngeal nerves to the cough center
  • Cough center
    • It is located in the medulla
    • It receives impulses from the cough receptors and initiates cough
  • Efferent pathway
    • Nerves carry efferent impulses to the abdominal muscles, intercostal muscles, diaphragm, glottis and vocal cords
  • Sequence of events in cough
    • There is an initial deep inspiration
    • Then the glottis and vocal cord closes
    • The diaphragm relaxes
    • The abdominal muscles and intercostal muscles contract
    • The pressure within the lungs builds up – upto 100mm of Hg
    • The glottis and vocal cords open resulting in a rapid release of air under pressure – speeds of upto 100 miles/hour
    • The sound produced is due to the turbulent flow
    • It helps to remove any irritant substances from the respiratory system
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