human brain

[sonar]

human brain require glucose for its fuction and in our body glucose is stored in the form of glycogen in the liver and muscles so at the time of fasting our brain is totaly dependent on liver for glucose availability so why not our brain stores glucose for its own purpose? infact brain has large amount of lipid surrounding nerve tissues so why not brain stores glucose in the form of lipid ( which has high calori value compair to glucose)and use?