Final answer:
The maximum amount of air that can be moved in or out of the lungs in one breath is defined as respiratory volume, involving active inhalation and passive exhalation processes dictated by pressure differences.
Step-by-step explanation:
The term used to describe the maximum amount of air that can be moved in or out of the lungs in a single respiratory cycle is known as respiratory volume. This includes various components such as the amount of air inhaled during a normal breath, the amount of air that can be exhaled after a normal exhalation, and the air left in the lungs after a forced exhalation. The ability to breathe—to have air enter the lungs during inspiration and leave during expiration—is dependent on the pressure differences between the atmosphere and the lungs. Breathing, also referred to as ventilation, consists of two steps: inhalation and exhalation. Inhalation is an active process primarily due to the contraction of the diaphragm, a large, sheet-like muscle situated below the lungs. When the diaphragm contracts, it increases the chest volume and decreases air pressure inside the lungs, causing air to rush in. Exhalation is a passive process that mainly results from the diaphragm relaxing and the chest cavity decreasing in size, which increases the air pressure inside the lungs and forces air out.