Final answer:
Decongestants in cough medicines help relieve congestion in the respiratory system by constricting blood vessels in the nasal passages. This clears the airways and makes breathing easier. Phenylephrine is a common decongestant that dilates the bronchioles of the lungs, allowing mucus to be cleared.
Step-by-step explanation:
Decongestants play a role in cough medicines by helping to relieve congestion in the respiratory system. They work by constricting the blood vessels in the nasal passages, which reduces swelling and clears the airways.
For example, phenylephrine is a decongestant commonly found in cough medicines. It binds to specific receptors in the bronchioles of the lungs, causing them to dilate and allowing mucus to be cleared from the lower respiratory tract.
Overall, decongestants help alleviate symptoms such as a runny nose and nasal congestion, making it easier to breathe and reducing the need to cough.