4.2 Explain the processes for redistributing blood during exercise.

When you exercise, the blood vessels dilate and the blood is able to flow better. As energy gets used up by your muscles, the muscles produce carbon dioxide. By products cause the capillaries within the muscles to expand and increased blood flow delivers more oxygenated blood to the working muscles.When your body becomes under pressure from exercise, blood that would have gone to other organs goes to the muscles instead. This happens by the sympathetic nervous system stimulating the nerves to the heart and blood vessels, this causes blood vessels (arteries and veins) to contract and constrict. The vasoconstriction reduces blood flow to tissues and concentrates on the muscles (http://health.howstuffworks.com/sports-physiology9.htm).