Cerebral blood flow – The blood supply or flow to the brain in a given time. Normally it is 750 millitres per minute or 15% of the cardiac output in an adult. The CBF is greater in children (2 fold increase) and decreases by adolescence (1.5 fold increase). CBF can be calculated by dividing the cerebral perfusion pressure by the cerbrovascular resistance. Cerebrovascular resistance is controlled by four major mechanisms: the brain’s metabolic activity (or ‘metabolic autoregulation’), autoregulation of pressure, chemical control (by arterial pCO2 and pO2)and neural control.