The Marathon Runner: Oxygen and CO₂ Levels During Exercise

During exercise, how does oxygen concentration in arterial blood compare to venous blood?

• Same in both

• Higher in arterial blood

• Higher in venous blood

• Neither has oxygen

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Why is oxygen concentration lower in venous blood during exercise?

• Lungs are not working as hard

• Arteries don’t carry oxygen

• Blood is moving too fast

• Muscles are using more oxygen for energy

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Arterial blood delivers oxygen-rich blood to the body, while venous blood carries oxygen-poor blood back to the heart.

• True

• False

What happens to CO₂ concentration in venous blood during exercise?

• Decreases

• Increases

• Stays the same

• Disappears

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Why does CO₂ concentration increase in venous blood during exercise?

• Lungs are producing CO₂

• Blood can’t hold oxygen

• Muscles are producing more CO₂ as waste during respiration

• Brain sends more signals

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The main waste product of cellular respiration that leaves the muscles during exercise is carbon dioxide.

• True

• False

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Why is arterial O₂ concentration stays fairly stable during exercise?

• Arterial blood comes directly from the lungs

• Arterial blood comes from the muscles

• Arterial blood is mixed with venous blood

• Arterial blood doesn’t carry gases

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Why do you breathe faster when you sprint? (pick 2)

• To get more O₂ into the blood

• To make your heart beat faster

• To cool your body down

• To remove CO₂ faster

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Looking at the graph, which line represents arterial O₂ concentration?

• The line that stays mostly flat and high

• The line that decreases during exercise

• Both lines drop at the same rate

• Neither line changes

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According to the graph, what happens to venous O₂ concentration as exercise increases?

• It increases

• It decreases

• It stays the same

• It rises, then falls