MCAT Biological and Biochemical Foundations of Living Systems Practice Exam

The volume of air inhaled or exhaled during a normal breath is known as tidal volume. This term specifically refers to the amount of air that is exchanged with each normal respiratory cycle, which is typically about 500 milliliters in a healthy adult at rest. Tidal volume represents the baseline respiratory activity that occurs during regular, unconscious breathing.

Other options present terms related to lung volumes that are important in understanding respiratory physiology, but they represent different aspects. For example, residual volume is the amount of air remaining in the lungs after a maximal exhalation. Vital capacity refers to the maximum amount of air a person can expel from the lungs after a maximal inhalation, and it is the sum of tidal volume, inspiratory reserve volume, and expiratory reserve volume. Lastly, expiratory reserve volume is the additional amount of air that can be forcibly exhaled after the end of a normal expiration. Each of these volumes plays a critical role in respiratory function, but they are not representative of the volume exchanged during regular, continuous breathing like tidal volume is.