Q4. Assertion: air enters the lungs during inspiration. Reason: the intra-pulmonary pressure falls below atmospheric pressure. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion (NCERT page 186).
Q5. A person’s TV is 500 mL, IRV 3000 mL, ERV 1100 mL and RV 1200 mL. Find the vital capacity and the total lung capacity.
VC = ERV + TV + IRV = 1100 + 500 + 3000 = 4600 mL; TLC = VC + RV = 4600 + 1200 = 5800 mL (NCERT page 187).
Q6. Which capacity is the volume of air left in the lungs after a normal expiration, and which volumes make it up?
The functional residual capacity, ERV + RV (NCERT page 187).
Q7. How can the strength of inspiration and expiration be increased?
NCERT mentions additional abdominal muscles (page 186). Anatomically, abdominal contraction assists forced expiration, while accessory inspiratory muscles, including neck muscles, assist deeper inspiration (NHLBI, “How Your Body Controls Breathing”).