Question

Which of the following statements about the mechanism of ventilation/breathing is incorrect?

• A. As the diaphragm relaxes, air is expelled from the respiratory system.
• B. During inspiration the lungs act as suction pump.
• C. Inspiration is a passive and expiration is an active process.
• D. For quiet breathing, external intercostal muscles and diaphragm play an important role.

Answer 1

The correct option is C Inspiration is a passive and expiration is an active process.

Inspiration is an active process while expiration is a passive process. During inspiration the thoracic cage moves upward and forward to increase the volume of thoracic cavity, this contraction is brought about by the activity of the external intercostals, intercondrial intercostals that elevate the ribs, the diaphragm also achieves a dome shape. Here, the contraction of the muscles to pull the ribs and the diaphragm upwards requires energy. Hence, an active process

During expiration the contracted muscles relax, hence a passive process.

So, the correct answer is 'Inspiration is a passive and expiration is an active process.'