HOTS Science Primary 5 Systems

Ravi measured his heart rate before, during, and after running. He noticed his heart rate increased significantly during the run. What is the main reason for this increase?

A To take in more oxygen from the surroundings.
B To cool down the body through increased blood flow.
C To help the lungs expand and contract more quickly.
D To transport more oxygen and digested food to the muscles faster.
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Worked Solution

Step 1: During exercise, muscles need more energy. Step [2-9]: More energy requires more oxygen and food for respiration. Step [2-9]: The heart pumps faster to increase the speed at which these materials reach the muscle cells and to remove waste CO2 faster.

Correct answer: To transport more oxygen and digested food to the muscles faster.

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