Question

Mark the true statement among the following with reference to normal breathing.

• A. Inspiration is a passive process whereas expiration is an active process
• B. Inspiration is an active process whereas expiration is passive process
• C. Inspiration and expiration are active processes
• D. Inspiration and expiration are passive processes

Answer 1

The correct option is B Inspiration is an active process whereas expiration is passive process

Inspiration is an active process whereas expiration is a passive process. Inspiration occurs when the muscles of diaphragm contract to increase the overall volume of thoracic cavity. Thus the pressure within the lungs (intrapulmonary pressure) is less in comparison to the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure. As the muscles use energy for contraction, inspiration is called an active process. Whereas, during the expiration diaphragm muscles relax (without the use of energy) and intra-pulmonary pressure becomes higher than the atmospheric pressure and air rushes out. Thus, it is a passive process.