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Q10 - Pressure and Volume Changes During Breathing

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Respiratory Physiology

Animal Anatomy and Physiology

The graph below illustrates the pressure and volume changes during breathing.

Graph with left axis Hgmm (750–765) and right axis cm³ (2500–3000), x-axis split into phase I and phase II by a dashed vertical line. Curve A oscillates around 760: dips slightly during phase I, rises to a peak (~763) during phase II, then returns to 760. Curve B stays in the 755–758 range throughout, always below 760. Curve C rises from ~751 to ~760 during phase I, then falls steadily to 750 by the end of phase II. Fig.1.

Identify what is represented by letters A, B and C, and the Roman numerals I. and II. Match these symbols (A–C and I–II) with the descriptions below. Every symbol matches one description only, but there are descriptions that do not match any of those - mark those as “No match”.

Q10.1. The graph shows three curves (A, B, C) and two phases (I, II) during a breathing cycle. Every symbol matches at most one description below; some descriptions match none of the symbols (mark those "no match"). What matches "volume changes of the intrapleural space during breathing"?
Q10.2. What matches "inhalation phase of breathing"?
Q10.3. What matches "pressure change in the lungs (alveolar pressure) during breathing"?
Q10.4. What matches "pressure change in the left ventricle of the heart during breathing"?
Q10.5. What matches "pressure change of the intrapleural space during breathing"?
Q10.6. What matches "volume change of the lung during breathing"?
Q10.7. What matches "exhalation phase of breathing"?
Q10.8. What matches "volume change of the abdominal cavity during breathing"?
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Question reproduced from IBO 2019, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Official answer key