Standard Science Primary 5 Systems

Siti went for a 2.4km run. Which of the following correctly describes the changes in her heart rate and breathing rate?

A Both heart rate and breathing rate remained the same.
B Only heart rate increased while breathing rate remained the same.
C Heart rate increased while breathing rate decreased.
D Both heart rate and breathing rate increased.
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Worked Solution

Step 1: During exercise, the muscles need more energy. Step [2-9]: To produce more energy, the body needs more oxygen and must remove carbon dioxide faster. Step [2-9]: This leads to an increase in both breathing rate (to take in O2) and heart rate (to transport O2 and digested food to muscles).

Correct answer: Both heart rate and breathing rate increased.

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