The respiratory system is oxygen inhaled into the body and oxygen exhaled from the body. The oxygen is carried throughout all the body systems by blood through the blood vessels. The blood is then pumped by the heart. When a person is resting the blood pumps 5 liters of blood, when the person is exercising the heart pumps 7 times the amount of blood.
The amount of air you breathe depends on how active you are. When you start to move around and exercise the muscles in your body send messages to your brain telling you that they need more oxygen. …
