Final answer:
The statement that the diaphragm contracts during inhalation resulting in lower alveolar pressure than atmospheric pressure, and relaxes during exhalation resulting in higher alveolar pressure than atmospheric is true. Inhalation is an active process while normal exhalation is typically passive.
Step-by-step explanation:
The student's question refers to the processes of inhalation (inspiration) and exhalation (expiration) and the role of the diaphragm and alveolar pressure in these processes. The statement provided is true. During inhalation, the diaphragm contracts, the chest expands and the alveolar pressure is reduced to less than atmospheric pressure, causing air to flow into the lungs. This is because the movement of the diaphragm downwards increases the thoracic cavity volume, leading to a drop in internal pressure compared to the external atmosphere. Conversely, during exhalation, the diaphragm relaxes and moves upwards, resulting in decreased thoracic cavity volume, which increases the alveolar pressure to above atmospheric pressure, forcing air out of the lungs. The process of normal expiration is typically passive as it is mainly driven by the elasticity of the lungs and the relaxation of muscles.