Mechanism of Breathing · NCERT Biology

Which of the following events occurs during the process of inspiration?

  1. Relaxation of the diaphragm
  2. Contraction of external intercostal muscles
  3. Decrease in the volume of the thoracic chamber
  4. Relaxation of the internal intercostal muscles only
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Correct answer: Contraction of external intercostal muscles

Contraction of the external intercostal muscles lifts up the ribs and the sternum, causing an increase in the volume of the thoracic chamber in the dorso-ventral axis. This is a key step in increasing pulmonary volume for inspiration.

Difficulty: Medium Question 2 of 20

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