Question

which causes most of the pressure changes that result in inhalation and exhalation?
a.) contraction and relaxation of the intercostal muscles only
b.) contraction and relaxation of the lungs.
c.) contraction and relaxation of the diaphragm only.
d.) contraction and relaxation of the diaphragm and intercostal muscles

Explanation:

During inhalation, the diaphragm contracts and moves downward, while the intercostal muscles contract to expand the ribcage. This increases the volume of the thoracic cavity, reducing pressure inside the lungs compared to the outside, causing air to rush in. During exhalation, the diaphragm and intercostal muscles relax. The diaphragm moves back up, and the ribcage recoils, decreasing the thoracic cavity volume. This increases pressure inside the lungs, forcing air out. The lungs themselves do not actively contract or relax (they are passive in this process due to their elastic nature and the pressure changes caused by the diaphragm and intercostal muscles).

Answer:

d. Contraction and relaxation of the diaphragm and intercostal muscles