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I've heard that the brain consumes quite a lot of oxygen and energy, compared to the rest of the body. What I'm interested in is if this is the kind of energy and oxygen that the rest of the body competes for?

  • For example, does running divert resources from the brain to the muscles, leading to decreased cognitive performance?
  • Does digesting food divert resources from the brain to the gut?

Does the heart rate or blood pressure have anything to do with how much resources, like oxygen and energy are available to neurons?

Thank you for your input!

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Running involves quite a bit of brain resources. Coordination, balance, obstacle avoidance, etc.. So the total energy requirement for running would have to include the need of the muscles and the brain or running wouldn't occur. –  KennyPeanuts Nov 11 '12 at 18:48
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up vote 3 down vote accepted

You can grab any university level text on human physiology and you will find that the brain is a unique organ for cellular respiration. The brain is only capable of using two metabolic subtrates: glucose for oxidative phosphorylation (producing ATP) and ketone bodies.

Exercise does indeed divert blood flow toward the muscles. After all, they are undergoing higher levels of respiration and need nourishment. Your body will always balance muscular needs and the needs of the brain and the rest of the body. Similarly, digesting food has a similar response, although this is more involved. Eating food has a autonomic reflex to increase blood flow to the stomach and digestive tract to facilitate the processing and distribution of nutrients.

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Diverting blood to the gastrointestinal tract doesn't necessarily mean that less blood flows to the brain - it could be other organs that are "deprived". And even if blood flow to the brain were to be reduced this doesn't mean that the supply of glucose would become limiting in any way since the difference between arterial and venous blood glucose is quite small - the brain would just need to extract more glucose from the blood that was available. –  Alan Boyd Nov 10 '12 at 22:08
    
Quite right. I should have clarified that I did not mean to imply that the brain is deprived, just that the pattern of blood flow changes. –  leonardo Nov 11 '12 at 12:31
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While in general the answer is "yes", the brain does use the same type of resources as other parts of the body, you cannot from that alone derive conclusions about the brain competing with other organs. Also, I think that cognitive performance is not a function of availability of resources. In fact, the moment that the brain lacks crucial resources like oxygen, it simply shuts down. But you don't faint when you start running (if you do, go see a doctor). "Power-saving mode" for the brain is not "reduce IQ by 20 points", but "just make sure the body is breathing and shut down everything else".

Also, I do not think that digesting food requires any comparable amount of energy that it would require the brain to give up on some of the oxygen it needs.

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