Respiratory System MCAT Practice Question
A 68-year-old man with COPD presents to the pulmonary clinic for evaluation of dyspnea on exertion. Pulmonary function tests show significantly reduced FEV1 and FVC. During exercise testing, he demonstrates increased use of accessory muscles (scalene and intercostal muscles) compared to healthy controls. A neurologist explains that during exercise, his ventral respiratory group (VRG) neurons are being recruited to facilitate more forceful breathing. Which of the following best explains the functional advantage of this brainstem organization during exercise in this patient?
Answer choices
- AThe dorsal respiratory group (DRG) and VRG are completely redundant, allowing either group to independently generate all breathing patterns needed during rest or exercise
- BThe DRG mediates quiet breathing through inspiratory neurons, while the VRG recruits both inspiratory and expiratory neurons to enable forceful breathing and active expiration during exerciseCorrect answer
- CThe VRG is responsible for all expiratory efforts, whereas the DRG exclusively controls inspiration; they function antagonistically to prevent simultaneous contraction
- DThe DRG controls all aspects of respiration, while the VRG only processes chemoreceptor signals for O2 and CO2 sensing to adjust breathing rate
- EExpiration is entirely passive and requires no neural control; the DRG and VRG are both exclusively inspiratory groups that differ only in their anatomic location
- FThe VRG provides tonic inhibition of the DRG during exercise to prevent hyperventilation and excessive respiratory muscle fatigue
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.