Final answer:
Drugs used to treat conditions like asthma by dilating airways work by stimulating adrenergic receptors, specifically α-adrenergic receptors, with drugs like phenylephrine acting as an agonist.
Step-by-step explanation:
The drugs used to dilate bronchial airways are known as sympathomimetic drugs. These medications generally interact with adrenergic receptors to produce their effects. There are two primary types of these receptors: α-adrenergic and β-adrenergic. Phenylephrine is a well-known sympathomimetic drug that binds to α₁-adrenergic receptors, leading to the dilation of bronchioles and the clearance of mucus from the lower respiratory tract, thereby providing relief for conditions such as asthma. Medications like phenylephrine imitate the action of the body’s catecholamines, adrenaline, and noradrenalin, which are natural ligands for the adrenergic receptors, particularly during the sympathetic ‘fight-or-flight’ response. Conversely, sympatholytic drugs would block this receptor activity, inhibiting the sympathetic effect on its target organs.