What are the structures or what's involved in blood pressure control in the brain of a giraffe? URL please.?

What are the structures or what's involved in blood pressure control in the brain of a giraffe? URL please.What are the structures or what's involved in blood pressure control in the brain of a giraffe? URL please.?
http://www.wikinfo.org/index.php/Giraffe





Many more subtle modifications to the Giraffe's structure have evolved, however, particularly to the circulatory system. A Giraffe's heart, which can weigh up to 24 lb (10 kg), has to generate around double the normal blood pressure for a large mammal in order to maintain blood flow to the brain against gravity. In the upper neck, a complex pressure-regulation system called the rete mirabile prevents excess blood flow to the brain when the Giraffe lowers its head to drink. Conversely, the blood vessels in the lower legs are under great pressure (because of the weight of fluid pressing down on them). In other animals. such pressure would force the blood out through the capillary walls: giraffes, however, have a very tight sheath of thick skin over their lower limbs which maintains high extravascular pressure in exactly the same way as a pilot's g-suit.