Circulation & Breathing Together

Question 1

Jordan counted his pulse while sitting quietly and got 80 beats per minute. After 3 minutes of doing fast skipping rope, he counted his pulse again and got 118 beats per minute. Which explanation best tells why Jordan’s heart beat faster after skipping?

Accepted Answer

His muscles were using more oxygen, so the heart had to pump blood faster to deliver the extra oxygen.

Answer

His skin needed to stay cool, so the heart sent more blood to the surface to release heat.

Answer

His heart got tired from the activity, so it started beating faster to catch up.

Answer

His lungs were blowing out extra air, which made the heart beat faster automatically.

Question 2

Liam sits quietly and counts his pulse for one minute. He gets 68 beats. Then he does three minutes of jumping rope and counts his pulse again, getting 102 beats. Which explanation best describes why Liam’s heart rate is higher after jumping rope?

Accepted Answer

His muscles are using more oxygen, so his heart must pump more blood to deliver the extra oxygen and take away carbon‑dioxide.

Answer

His heart grew larger during the jumping, so it has to beat faster to fill the bigger chamber.

Answer

His brain tells the heart to beat faster just to keep him awake after the activity.

Answer

The extra oxygen he breathed in stays in his lungs, so the heart has to beat faster to push the same amount of blood through.

Question 3

Leo takes a big breath and then runs to catch a ball. Which statement correctly describes how the oxygen he inhaled reaches his leg muscles and how the carbon‑dioxide produced by those muscles gets back to his lungs?

Accepted Answer

Oxygen enters Leo’s lungs, diffuses into the blood, the heart pumps this oxygen‑rich blood through arteries to his leg muscles; the muscles use the oxygen and put carbon‑dioxide into the blood, which returns to the heart via veins and then travels to the lungs to be breathed out.

Answer

Oxygen goes straight from Leo’s lungs through tubes to his leg muscles; the muscles use the oxygen and send carbon‑dioxide directly back to the lungs without the blood or heart being involved.

Answer

The heart makes oxygen, sends it to the lungs where it mixes with carbon‑dioxide, and the mixture is then sent to the muscles.

Answer

Oxygen travels from the lungs to the heart, which first sends it to the brain; the brain uses the oxygen and passes the carbon‑dioxide to the leg muscles, which then send it to the lungs.

Try three questions

Jordan counted his pulse while sitting quietly and got 80 beats per minute. After 3 minutes of doing fast skipping rope, he counted his pulse again and got 118 beats per minute. Which explanation best tells why Jordan’s heart beat faster after skipping?

Liam sits quietly and counts his pulse for one minute. He gets 68 beats. Then he does three minutes of jumping rope and counts his pulse again, getting 102 beats. Which explanation best describes why Liam’s heart rate is higher after jumping rope?

Leo takes a big breath and then runs to catch a ball. Which statement correctly describes how the oxygen he inhaled reaches his leg muscles and how the carbon‑dioxide produced by those muscles gets back to his lungs?

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