1 6 4 7 3 10 5 9 2 8 When I started to run up and down the stairs… This was detected by my brain which sent nerve impulses to the heart. The heart started to beat faster and harder to move my blood faster. Glucose reacted with oxygen, releasing energy. At the same time, carbon dioxide and water were produced. The energy needed for this was replaced by a chemical reaction in the muscle cells called respiration. My heart rate went back to normal. Very soon, my muscle cells started to run short of oxygen and acidic carbon dioxide started to build up in the blood. My heart and blood system was able to supply enough oxygen to the muscle cells. When I stopped running up and down the stairs, the respiration in my muscle cells slowed down. My leg muscles contracted to lift my body. 1 6 4 7 3 10 5 9 2 8

What does it mean to be fit? If you are fit, your body is well set up for exercise. For exercise your muscle cells need energy. Where does this come from? energy water carbon dioxide respiration glucose oxygen Which organ systems provide the things you need for respiration?

Why does your pulse change when you do some activities? Which activity gave the highest pulse rate? What sort of activity would give you a higher pulse rate? What might you be doing if you had a lower pulse rate? When your heart is beating faster, what is happening in your body? Why do different people have different pulse rates?

What process is this animation showing? Where is it happening? How is this linked to fitness and stamina?