Final answer:
The expiratory reserve volume (ERV) is also called residual volume. It is the amount of additional air that can be exhaled after a normal exhalation. The residual volume is important for maintaining respiratory gas balance.
Step-by-step explanation:
The expiratory reserve volume (ERV) is also called residual volume. It is the amount of additional air that can be exhaled after a normal exhalation. The residual volume is important for preventing the lungs from completely emptying and helps maintain respiratory gas balance.