Chapter 41.1, Problem 1CS

Core Skill: Modeling The goal of this modeling challenge is to draw a model showing how smooth muscle contraction affects the width of a tube such as a bronchiole.

Modeling Challenge: Smooth muscle often surrounds tubelike structures in animal bodies, where it controls the degree to which the tubes are opened. In the disease asthma, smooth muscle tissue in the small air tubes called bronchioles is sometimes in a highly contracted state. Shown below is a model of a fully opened bronchiole in a human. Draw another model of the bronchiole as you think it will appear when the person is experiencing asthmatic symptoms (contracted smooth muscle tissue). Referring to your model, explain why individuals with asthma have difficulty breathing when their symptoms flare up.

A healthy bronchiole in a human lung. Note that the smooth muscle tissue is in a relaxed state, and the bronchiole is fully opened.