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