Select the correct events that occur during
inspiration.
A. Contraction of diaphragm
B. Contraction of external inter-costal muscles
C. Pulmonary volume decreases
D. Intra pulmonary pressure increases
Explanation:
During inspiration, the diaphragm contracts and flattens, and the external intercostal muscles contract to raise the ribs. This enlarges the thoracic cavity, increasing pulmonary (lung) volume. As a result, intra-pulmonary pressure falls below atmospheric pressure, allowing air to flow into the lungs. Therefore, A and B are correct, while C (volume decreases) and D (pressure increases) are incorrect.
🧠 Did You Know?
Inhalation involves active muscular work; exhalation at rest is mainly a passive process where the diaphragm and intercostals relax, pushing air out as the chest cavity returns to its smaller volume.
💡 NCERT Memory Line:
During inspiration, rib cage moves up and out; diaphragm contracts to increase thoracic volume, causing a decrease in intra-pulmonary pressure.
