Nerve cells in the brain use vast amounts of energy, but can't store much fuel. Instead, fuel is transported to them along a vast web of blood vessels, which would stretch 400 miles long if spread out end to end. The web consists of large arteries (here white, in a mouse brain) that wind across the brain’s surface before penetrating into its depths and branching into smaller capillaries (red). These vessels constantly adapt to the changing energy demands of different brain regions. When a region is active, the nearby blood vessels will widen to allow extra blood and the fuel it carries to reach the area. However, scientists have not fully understood how the nerve cells and vessels communicate. Now research suggests that capillaries can detect the activity levels of cells. When they sense an increase, they send a signal that prompts upstream blood vessels to widen and increase blood flow.
Written by Deborah Oakley
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