When does inhalation stop during breathing?

Inhalation stops during breathing when it reaches a pressure equilibrium. This occurs when the internal pressure within the lungs equals the atmospheric pressure outside. The respiratory system regulates breathing to maintain this pressure balance, which is crucial for effective airflow and gas exchange. When the lung volume increases during inhalation, air flows in until the lung pressure matches the external pressure.

The other options do not fully capture the physiological basis for why inhalation ends. While the sensation of having "full" lungs may influence the urge to exhale, the actual triggering mechanism is based on pressure balance rather than subjective fullness. Similarly, the initiation of speech does not dictate the end of inhalation; rather, it's the transition to exhalation when airflow needs to be managed for sound production. Lastly, alterations in vocal fold tension may play a role in speech but are not directly related to the mechanical process of stopping inhalation. Thus, the mechanism of pressure equilibrium is the most accurate and relevant explanation for when inhalation stops.