Question

Expiratory muscles contract at the time of

A

Deep inspiration

B

Normal inspiration and expiration

C

Forceful expiration

D

Normal expiration

Medium
Solution
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Correct option is C)

During quiet breathing, there is little or no muscle contraction/relaxation involved in expiration. This process is simply driven by the elastic recoil of the lungs in healthy individuals. In certain conditions the elasticity of the lung can be lost, such as in emphysema. Forced or active expiration occurs in such individuals as well as occurring during exercise. The abdominal muscles and the internal and innermost intercostal muscles help expel air.

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