Various organs related to the respiratory system control the breathing process through reflex action. For example-
(i) Tension receptor cells in the lung wall are stimulated when the lungs are filled with air during inhalation. This stimulation reaches the anesthetic center via the vagus nerve and dampens the activity of this center. As a result, breathing stops. Wall tension receptor cells are not stimulated as the lungs contract during exhalation. It activates the anesthetic center and causes respiration. The reflex action caused by the contraction and expansion of the lungs is called the Herring-Breyer reflex.
(ii) Stimulation of the mucous membrane of the nasal cavity through the olfactory nerve produces a reflex action and changes breathing.
(iii) When a foreign substance enters the trachea, the mucous membrane is stimulated, triggering the coughing reflex through the vagus nerve and altering breathing.
(iv) Stimulation of pharyngeal wall during swallowing of food causes Gag reflex action through glossopharyngeal nerve and stop respiration.
(v) Stimulations from the skin, muscles, viscera, joints etc. of the body regulate respiration by inducing reflex action.