Question

Inspiration occurs when

• A. the volume of the lung increases while the pressure in the lung decreases
• B. the volume of the lung decreases while the pressure in the lung increases
• C. the volume of the lung increases while the pressure in the lung increases
• D. the volume of the lung decreases while the pressure in the lung decreases

Answer 1

Answer: (A)

Breathing constitutes inspiration and expiration processes. This depends on Boyle's law. It states that pressure is inversely proportional to volume when the temperature remains constant (P $\alpha $ 1/V). Pressure here is the partial pressure as it involves the pressure of one gas in the atmosphere. During inspiration, oxygen from the atmosphere enters the lungs thus volume of the lung cavity should be more which means pressure should be less. External intercostal muscles and diaphragm causes the volume to increase and pressure to decrease and thus inspiration takes place.