Fuels and energy metabolism in the brain

In the fed state, the only fuel used by the brain is glucose, derived from the blood. In prolonged starvation or chronic hypoglycaemia, ketone bodies are nsed which rednce the rate of utilisation of glucose by the brain bnt, even so, glucose still provides about 50% of the energy. Consequently, under all conditions, maintenance of the blood glucose concentration is essential for the function of the brain the mechanisms that are responsible for this are discnssed in Chapters 6, 12 and 16. 

The brain takes up glucose and oxygen in stoichiometric amonnts which indicates that glucose is completely oxidised to CO2. However, this does not mean that lactate is 

From arteriovenous difference, the utilisation of glucose by human brain is approximately 0.32 mmol/min which, if completely oxidised would consume (6 x 0.32) or 1.92 mmol/min of oxygen. The rate of oxygen uptake by the human brain is also measured from arteriovenous difference it is 2.1 mmol/min (i.e. very close to that calculated, 1.92). 

The traditional model for the processes by which glucose is made available for the neurones is that glucose is transported across the blood-brain barrier into the extracellular fluid, from where it is taken up by neurones (and gUal cells). However, there are several problems with this model  

Disorders of the brain affect a very large number of people. It is estimated that about one in five women and one in seven men in the UK suffer from mental illness. The biochemical causes include the following  

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