What physiological function is particularly sensitive to altitude changes?

Breathing is the physiological function that is particularly sensitive to altitude changes due to the decreased availability of oxygen at higher elevations. As altitude increases, the atmospheric pressure drops, which in turn reduces the partial pressure of oxygen in the air. This can lead to various physiological effects, such as hypoxia, where the body does not receive enough oxygen for essential functions.

At sea level, the body efficiently absorbs enough oxygen from the air for metabolic needs. However, as altitude increases, the body struggles to maintain sufficient oxygen levels, causing an increase in breathing rate and depth in an attempt to compensate for the lack of oxygen. This sensitivity of the respiratory system to changes in altitude is a foundational aspect of human physiology that impacts performance and can lead to altitude sickness if the body fails to acclimatize.