One set of astrocytic processes ensheaths the vasculature and a second set reaches toward the synapse, the site of highest energy demand ( Harris et al. Although oxygen diffuses freely into the parenchyma, glucose and other hydrophilic energy substrates are translocated across membranes via specific transporter proteins ( Fig. 2013) to ensure adequate delivery of oxygen and glucose. The microvasculature consists of a complex and dense network of highly interconnected blood vessels ( Weber et al. A special microarchitecture has evolved to support this extreme need, in which glial cells play a central role ( Fig. Although the brain accounts for merely 2% of body weight, it receives ∼15% of cardiac output, and uses 20% of the oxygen and 25% of the glucose of the total body turnover ( Magistretti 2008). The energy requirements of the central nervous system (CNS) are very high compared with those of other organs.
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