Which pressure remains negative throughout the respiratory cycle?

Correct Answer: B

Rationale: The correct answer is B: intrapleural pressure. Intrapleural pressure remains negative throughout the respiratory cycle due to the opposing forces of the elastic recoil of the lungs and the chest wall. This negative pressure keeps the lungs inflated and facilitates breathing. In contrast, intrapulmonary (A) and intra-alveolar (C) pressures fluctuate during inhalation and exhalation, becoming positive and negative, respectively. Atmospheric pressure (D) remains relatively constant and serves as the reference point for pressure changes in the respiratory system.

Correct Answer: B

Rationale: The correct answer is B: changes in PCO2. Chemoreceptors in the carotid and aortic bodies detect levels of oxygen, carbon dioxide, and pH in the blood. Blocking afferent action potentials from these chemoreceptors would specifically interfere with detecting changes in PCO2, as these receptors primarily respond to alterations in CO2 levels. This interference would disrupt the brain's ability to regulate breathing in response to changes in PCO2, leading to potential respiratory problems. Choices A and C are incorrect because chemoreceptors primarily respond to CO2 levels, not O2 or pH. Choice D is incorrect because changes in blood pressure are primarily detected by baroreceptors, not chemoreceptors in the carotid and aortic bodies.

Correct Answer: A

Rationale: The correct answer is A: alveoli. The alveoli are not part of the bronchial tree; they are the tiny air sacs at the end of the bronchial tree where gas exchange occurs. The bronchial tree consists of the bronchi, terminal bronchioles, and respiratory bronchioles, which are responsible for conducting air into the lungs. Alveoli are located at the end of the respiratory bronchioles and are where oxygen is absorbed into the bloodstream and carbon dioxide is released. Therefore, alveoli are not considered part of the bronchial tree.

Correct Answer: A

Rationale: The correct answer is A: Trachea. Carina is the point where the trachea is divided into the left and right primary bronchi. This anatomical landmark is located at the lower end of the trachea where it bifurcates into the bronchi. The other choices, B: bronchi and C: larynx, are incorrect because the trachea is the structure that is divided at the carina, not the bronchi or larynx. Choice D: none of them is also incorrect because the trachea is indeed divided at the carina. Therefore, the correct answer is A as it accurately describes the anatomical location where the trachea divides.

Correct Answer: D

Rationale: The correct answer is D because during inhalation, the rib muscles and diaphragm contract, expanding the chest cavity which increases its volume. This decrease in pressure inside the lungs allows air to rush in. Therefore, all the actions mentioned in options A, B, and C occur during inhalation. Rib muscle and diaphragm contraction, increased volume in the chest cavity, and decreased air pressure collectively facilitate the process of inhalation. The other choices are incorrect because they do not encompass all the necessary actions that occur during inhalation.