Lungs and Heart: One Team

Science · The Human Body · ages 9-11

Name ______________________ Date ____________

After the heart pumps oxygen-rich blood to the body, what uses that oxygen?
- Only your lungs
- Your cells
- Only your bones
What do the lungs add to the blood?
- Oxygen
- Carbon dioxide
- Water
True or false: your heart beats faster during exercise because your muscles need more oxygen.
Circle one: True False
Leo's resting heart rate is 68 beats per minute. After running, it is 112 beats per minute. How many more beats per minute is that?
Answer: ______________
Start when the lungs add oxygen to blood. Put these stages in order: (1) heart pumps blood to the body, (2) lungs add oxygen to blood, (3) cells use the oxygen.
- 1, 2, 3
- 3, 2, 1
- 2, 1, 3
Why does your breathing rate go up at the same time as your heart rate during exercise?
- Muscles need more oxygen and make more carbon dioxide to remove
- Your lungs get tired and need a rest
- Your blood stops carrying oxygen
Ben checks his heart rate right after climbing stairs and finds it much higher than his resting rate from that morning. What is the best explanation?
- Climbing stairs stops his lungs from working
- His heart rate is always higher in the afternoon
- His muscles used more oxygen while climbing, so his heart pumped faster to supply it
Priya says: 'The heart pumps oxygen straight into my lungs, and then my lungs send it to my muscles.' What did she get backwards?
- She has it exactly right
- The lungs add oxygen first, then the heart pumps it to the muscles
- The muscles add oxygen to the lungs

Answer key

For grown-ups. Fold this page away before handing over the rest.

Your cells · Cells throughout your body use oxygen to release energy from food.
Oxygen · The lungs pick up oxygen from the air you breathe in and add it to your blood.
True · Working muscles use oxygen quickly, so the heart pumps faster to keep them supplied.
44 · 112 minus 68 equals 44 more beats per minute during exercise.
2, 1, 3 · Oxygen enters the blood in the lungs first, then the heart pumps it out, then cells use it.
Muscles need more oxygen and make more carbon dioxide to remove · Faster breathing brings in more oxygen and clears out the extra carbon dioxide your muscles produce.
His muscles used more oxygen while climbing, so his heart pumped faster to supply it · Exercise raises the demand for oxygen in muscles, so the heart pumps faster than it does at rest.
The lungs add oxygen first, then the heart pumps it to the muscles · Oxygen enters the blood in the lungs first. The heart then pumps that oxygen-rich blood out to the muscles.