Question

Assertion (A): During inspiration, the rib cage and sternum lift up, causing an increase in the volume of the thoracic cavity in the dorso-ventral axis. Reason (R): Due to relaxation of the diaphragm muscles, the volume of the thoracic cavity increases.

• A. Both (A) and (R) are correct, and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct, but (R) is not the correct explanation of (A).
• C. (A) is correct, but (R) is not correct.
• D. (A) is incorrect, but (R) is correct.

Hint:

Inspiration occurs when the diaphragm contracts and the thoracic cavity expands, leading to air intake.

Answer 1

The Correct Option is C

Step 1: Understanding the Mechanism of Inspiration
- During inspiration, the diaphragm contracts (not relaxes), increasing thoracic volume.
- The rib cage and sternum move upward, expanding the thoracic cavity.
- Reason (R) is incorrect since diaphragm relaxation leads to expiration.