Which of the following statements are correct?
(A) Intrathoracic pressure decreases during inspiration.
(B) Activation of pneumotaxic center stimulates inspiration.
(C) During expiration, pressure gradient operates from lungs to the atmosphere.
(D) Cavity of lungs decreases during expiration.
(E) Diaphragm contracts during expiration.
Select the correct option

Statement (A) is correct because during inspiration, the volume of the thoracic cavity increases, which leads to a decrease in intrathoracic pressure, allowing air to rush into the lungs.

Statement (B) is incorrect because the pneumotaxic center, located in the pons, sends inhibitory signals to the inspiratory center, thereby limiting inspiration and increasing the respiratory rate.

Statement (C) is correct because during expiration, the intrapulmonary pressure becomes higher than the atmospheric pressure, creating a pressure gradient from the lungs to the atmosphere.

Statement (D) is correct because during expiration, the relaxation of the diaphragm and external intercostal muscles reduces the volume of the thoracic cavity and the lungs.

Statement (E) is incorrect because the diaphragm relaxes and returns to its dome shape during expiration, whereas it contracts and flattens during inspiration.

Therefore, statements A, C, and D are correct.

Answer: A, C and D only