In order to expand the volume of the thoracic cavity during inhalation, what must occur?
a. the diaphragm moves upward
b. the ribs compress
c. inspiratory muscles relax
d. inspiratory muscles contract
Answer: d. inspiratory muscles contract
In order to expand the volume of the thoracic cavity during inhalation, the inspiratory muscles contract. When this happens, the diaphragm moves downward toward the abdomen and the rib cage is pulled up and outward.