Nutrition in the Brain
Some simple Facts about The Brain and Metabolism
- Weighs 2% of total body weight
- Recieves 15% of cardiac Output
- 20% of total body oxygen consumption
- 25% of total body glucose utilzatoin
The "Chim" Stoichiometric calculations
From a global blood flow of 57 ml/100 g·min, the brain extracts approximately 50% of oxygen and 10% of glucose from the arterial blood. Hence, the glucose utilization of the brain, as assessed by measuring the arterial–venous difference, is 31 mmol/100 g·min.
Oxygen consumption is 160 mmol/100 g·min; because CO2 production is almost identical, the respiratory quotient (RQ) of the brain is nearly 1, indicating that carbohydrates are the substrates for oxidative metabolism. Given a theoretical stoichiometry of 6 mmol of oxygen consumed for each mmole of glucose, glucose utilization by the brain should in theory be 26.6 mmol/100 g·min.
However, the measured glucose utilization is 31 mmol/100 g·min, indicating that an excess of 4.4 mmol/100 g·min of glucose follows other metabolic fates.
What has happened to the Missing Glucose?
Glucose can produce metabolic intermediates, such as lactate and pyruvate, which do not enter necessarily in the tricarboxylic acid cycle but rather can be released and removed by the circulation. Glucose can be incorporated into lipids, proteins, and glycogen, and it is also the precursor of certain neurotransmitters such as g-aminobutyric acid (GABA), glutamate, and acetylcholine (10, 60).
posted by Wiki Description @ 7:33 PM
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