Question

Your heart and lungs are active even when we sleep give reason

Answer 1

It is so because our body is full of metabolic activities and for that we need a good supply of oxygen as well as food.
Although the cerebrum and cerebellum of our brain will sleep but the medulla keep working for this.
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Answer 2

This is because we need oxygen every time for requirement of energy. (Heart) pumps the blood and lungs pumps oxygen all the time.