During exercise muscle cells need more energy. This is obtained from glucose by a process of aerobic respiration -
Oxygen + glucose ----> carbon dioxide + water (+ energy)
The respiratory system supplies oxygen and removes carbon dioxide.
The digestive system provides glucose.
The circulatory system carries the glucose and oxygen to the muscle cells and carries the carbon dioxide away to the lungs.
When you exercise your breathing rate and pulse rate increases because your cells need more carbon dioxide for respiration.
-Diaphragm contracts and moves…