Lamid sharks, such as the great white and mako, actively regulate their internal temperature and can even reach 20 degrees higher than their surrounding enviornment. They do this through a special arrangemnt of blood vessels. Cold oxygenated blood enters through the gills and passes by warm deoxygenated blood vessels. The warmth of the deoxygenated blood is transfered to the cold blood in this way. This mechanism is called counter currency. Heat is generated in large red muscle masses found at the midline of the shark. Red muscle is used for relatively slow, long duration periods of activity and will generate a lot of heat through its aeorbic metabolism. This differs from white mucsle, which is used for quick bursts of activity. Unfortunately white muscle tires very quickly. Thermoregulation is important for a shark due to its predatory nature. When an organism is cold, chemical reactions slow down. By maintaining a warm body, the shark is able to also maintain a rate of chemical reactions. This also improves the sharks awareness and its overall agility.