Question

during quiet breathing, one phase of ventilation is considered passive and one active. what doez that mean and why?

Answer 1

Inspiration (inhalation) is the process of taking air into the lungs. It is the active phase of ventilation because it is the result of muscle contraction. During inspiration, the diaphragm contracts and the thoracic cavity increases in volume. This decreases the intraalveolar pressure so that air flows into the lungs.

Expiration is typically a passive process that happens from the relaxation of the diaphragm muscle (that contracted during inspiration). The primary reason that expiration is passive is due to the elastic recoil of the lungs.