Which of the following statements is true regarding lung volumes?

Lung volumes are indeed influenced by pressure gradients, particularly during the process of ventilation. When inspiration occurs, the diaphragm and intercostal muscles contract, increasing the volume of the thoracic cavity. This increase in volume leads to a decrease in pressure within the lungs compared to the atmospheric pressure, allowing air to flow in. Conversely, during expiration, the muscles relax, causing the thoracic volume to decrease, which increases the pressure in the lungs and pushes air out.

Understanding that lung volumes can change based on the pressure differences around and within the thoracic cavity is crucial for understanding the mechanics of breathing and how various factors, including different muscle activations, influence lung function. This is why pressure gradients play a vital role in determining lung volumes during the respiratory cycle.

The other statements do not reflect the correct relationship between lung volumes and the factors that influence them. Access to muscle contraction is essential in changing lung volumes, and lung volumes are not static or solely dependent on oxygen levels.