Standard Science Primary 5 Systems

During heavy exercise, why does the heart beat faster?

A To pump oxygen and nutrients to the muscles more quickly.
B To produce more carbon dioxide for the lungs.
C To cool down the body temperature.
D To help the lungs expand more.
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Worked Solution

Step 1: Exercise increases the muscles' demand for energy. Step 2: Energy production requires more oxygen and glucose (nutrients). Step 3: The circulatory system must work harder to deliver these substances via the blood.

Correct answer: To pump oxygen and nutrients to the muscles more quickly.

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