Answer:
People who have asthma have a lot of difficulty breathing and when they do we can hear a sound coming from their chest. This is caused because there is a narrowing of the bronchial tubes. One of the causes of the narrowing of these airways is the contraction of the muscles around these tubes. When there is asthma, the contraction of these muscles causes the bronchial tubes to narrow more than normal.
The bronchial muscles are "involuntary" muscles, since they are muscles in our body over which we have no control. For example, we have no conscious control over heart muscle beats or stomach muscle contractions. Similarly occurs with the muscles around our bronchial tubes since they are under the control of our nervous system but are not controlled by the parts of the brain responsible for thinking.
Bronchodilators are medications that relax bronchial muscles. When these types of medications are used, the bronchial tubes dilate. When these muscles relax, the bronchial tubes open again and breathing usually returns to normal. On other occasions this does not happen because sometimes the bronchial tubes become inflamed and filled with mucus. In these cases, the bronchodilator will only provide partial relief for a moment as the tubes will remain blocked.
