What is the active component of respiration?

What is the active component of respiration?

• A. Expiration
• B. Inspiration
• C. Diffusion
• D. Circulation

Answer: (B)

Inspiration is the active part of respiration. It requires muscular work—primarily the diaphragm contracting to move downward and the external intercostal muscles lifting the ribs—expanding the thoracic cavity and creating a negative pressure that pulls air into the lungs. Expiration, especially at rest, is usually passive, driven by the lungs and chest wall returning to their resting size; active expiration happens mainly during forceful breathing, using abdominal and internal intercostal muscles to push air out. Diffusion is the gas exchange across the alveolar membrane and not a muscular action, while circulation refers to moving gases through the bloodstream, not into the lungs.

Inspiration is the active part of respiration. It requires muscular work—primarily the diaphragm contracting to move downward and the external intercostal muscles lifting the ribs—expanding the thoracic cavity and creating a negative pressure that pulls air into the lungs. Expiration, especially at rest, is usually passive, driven by the lungs and chest wall returning to their resting size; active expiration happens mainly during forceful breathing, using abdominal and internal intercostal muscles to push air out. Diffusion is the gas exchange across the alveolar membrane and not a muscular action, while circulation refers to moving gases through the bloodstream, not into the lungs.