Brain function requirements

Oxygen and glucose are essential to all tissues in the body as tissues require oxygen and glucose to function. Brain and nervous tissues use a disproportionally high amount of oxygen. In fact while the brain makes up about 2% of a bodies weight, it consumes 20% of the oxygen and 50% of the glucose in the body. Because these tissues require more oxygen and glucose to function, and because brain cells contain no glucose stores, they are more sensitive to changes in oxygen and glucose levels. If there was a lack of glucose in the brain, the brain tissue would be forced to use ketones in its place.