Figure 7: The origin of airway hyperresponsiveness is manifold. The factors that contribute to excessive airway responsiveness can be either inherent or acquired due to inflammatory and remodeling processes that take place in asthmatic lungs. In turns, the acquired defects can be either transient or more permanent. The transient defects are the ones responsive to treatments and are responsible for the variable component of AHR. The permanent defects are more refractory to current asthma therapies, and are responsible for part of the fixed (or hardly modifiable) component of AHR. See text for further detail.