airway tone may be influenced by circulating adrenaline and there is some evidence that adrenaline secretion may be impaired in asthma . beta-adrenoceptors ( which are almost entirely of the beta 2-subtype ) are localized to many cell types in airways and beta-agonist may be beneficial in airway obstruction , not only by directly relaxing airway smooth muscle ( from trachea to terminal bronchioles ) , but by inhibiting mast cell mediator release , by modulating cholinergic nerves , by reducing bronchial oedema and by reversing the defect in mucociliary clearance .
C0014563
adrenaline
C0001883
airway obstruction