浙一 The third basic principle. The cerebral blood flow(CBF) normally varies over a wide range (30-100 mL per 100g brain tissue per minute), depending on metabolic demand from neuronal activity within a particular area of the brainThe third basic principle: The cerebral blood flow (CBF) normally varies over a wide range (30-100 mL per 100 g brain tissue per minute), depending on metabolic demand from neuronal activity within a particular area of the brain