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How do irritant receptors in the airways protect the lungs from harmful substances?

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Medical illustration of the human chest showing the lungs, diaphragm, ribs, trachea, bronchus, and bronchioles, with one lung cut away to reveal internal structures. — human respiratory system The lungs serve as the gas-exchanging organ for the process of respiration.

Irritant receptors in the airways serve as a vital defense mechanism to protect the lungs from harmful substances. When these receptors are stimulated by noxious materials in the atmosphere, they trigger specific physiological responses designed to limit the entry of these agents into the bronchial tree.1

These protective actions include:

Airway Constriction: Stimulation causes the airways to narrow, which physically inhibits the penetration of injurious substances.1
Rapid Shallow Breathing: This change in breathing pattern further limits how deeply harmful agents can travel into the respiratory system.1
Coughing: Activation of these receptors also induces a cough, which is a critical reflex for clearing foreign material and secretions from the respiratory tract.12

These receptors are supplied by the vagus nerve and are also sensitive to various chemicals, including histamine, bradykinin, and prostaglandins.1