Which of the following describes active pressures in the respiratory system?

• A. Generated by passive recoil of the lungs
• B. Generated by the inspiratory and expiratory muscles
• C. Only generated during exercise
• D. Constant throughout the breathing cycle

Answer: (B)

Active pressures in the respiratory system are specifically associated with the efforts of the muscles involved in breathing, such as the diaphragm and intercostal muscles. These muscles contract to create pressure changes that facilitate the inhalation and exhalation processes. When these muscles are actively engaged, they generate active subglottic pressure that assists in phonation and regulates airflow during speech.

The other options do not accurately capture the nature of active pressures. For instance, passive recoil of the lungs refers to elastic forces that act when lung tissues return to their resting state after being stretched, which does not involve muscular effort. Moreover, active pressures are not exclusive to exercise; they are present in regular breathing patterns as well. Lastly, the pressures in the respiratory system fluctuate throughout the breathing cycle due to the actions of the respiratory muscles, varying during inspiration and expiration rather than remaining constant.