Functional Residual Capacity in Lungs — NEET Biology

Correct answer: B — S3 and S4

This question evaluates the definitions, calculations, and measurement methods of various respiratory capacities. S1: Inspiratory Capacity (IC) is indeed the total volume of air a person can inspire after a normal expiration, which includes tidal volume and inspiratory reserve volume (TV+IRV). This statement is correct. S2: Functional Residual Capacity (FRC) is the volume of air that will remain in the lungs after a normal expiration (ERV+RV). This statement is correct. S3: Vital Capacity (VC) is the maximum volume of air a person can breathe in after a forced expiration (ERV + TV + IRV). It can be calculated as Total Lung Capacity (TLC) minus Residual Volume (RV), not minus Expiratory Reserve Volume (ERV). This statement is NOT correct. S4: A spirometer measures volumes of air that can be exhaled or inhaled. Residual Volume (RV) is the volume of air remaining in the lungs even after a forceful expiration, which cannot be exhaled, and thus cannot be measured directly by a spirometer. Since FRC includes RV, FRC also cannot be directly measured by a spirometer. This statement is NOT correct. S5: A healthy human breathes 12-16 times/minute, with a Tidal Volume of approximately 500 mL. Therefore, the volume of air inspired or expired per minute is (12-16) * 500 mL = 6000-8000 mL. This statement is correct. Therefore, statements S3 and S4 are not correct. The final answer is B because S3 and S4 are incorrect based on the NCERT definitions and spirometry limitations.