The human brain has evolved compared with that of other vertebrates, yet we pay a substantial energetic bill for its use. This high-energy consumption is evidenced by some oft-cited values: despite being only 2-3% of total body weight, the brain receives 15% of cardiac output, and consumes ~20% of the body's oxygen, and 15% of total body glucose. But it is precisely this high-energy demand, married especially with a limited capacity for energy storage, that necessitates complex but effective regulation of regional blood delivery.
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