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How does brain activity affect energy usage?

  1. Aug 3, 2012 #1
    I'm curious to know how much energy a brain will use depending on the different activities it's doing.

    Sleeping vs. watching TV vs. doing rigorous physics problems vs. running a marathon

    For the above activities, what are the different energy requirements like?

    How do the things you're thinking about translate into energy usage?

    I assume the more active your brain is, the more electron transfer there will be, which means more energy will be required. I don't know details for any of this.
  2. jcsd
  3. Aug 3, 2012 #2


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    Staff: Mentor

    I'm not sure if exact studies have been completed for humans, but you can read this.


    The abstract - http://www.pnas.org/content/105/17/6409
  4. Aug 3, 2012 #3
    Interesting. Well I'm going to assume that the "housekeeping" energy demand is fairly constant regardless of usage. I'd guess that "housekeeping" would be more dependent on physical activity and surroundings (temp, humidity, etc).

    I can't read through the article right now, but one thing in the abstract stood out.

    It mentioned rat brain conditions used in the test.

    Would an anesthetized brain have any activity at all? I know it still tells the body to keep going, but as far as other electrical impulses go, would it be completely blank?
  5. Aug 3, 2012 #4


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    Gold Member

    neurontransmitters glutamate and GABA are the primary excitatory and inhibitory signals in the brain. These both are derived from glutamine, which is a big part of the body's energy system (through glucose). There's hundreds of biomolecular networks that lead to thing like transcription too. The CNS has a lot of work to do on the cellular level, some of it special to neurons, some to astrocytes, and they all integrate together with signaling in complex (and still not well understood) ways. Then there's also the electrical signals everybody things about when they think of CNS regulation.

    anesthetize just means to deprive one of consciousness. It does not shut down the brain so much as change it's state to a sleeping state. You definitely don't want to shut down your hindbrain, where autonomous functions are regulated. But the conscious parts of our brain, anyway, aren't the whole brain. Consciousness isn't a matter of a particular chunk of brain running, but how all the chunks of brain are working together. Unconsciousness, too, is just a matter of how all the chunks of brain are working together. Some parts get inhibited, some get excited, but nothing really completely shuts down. It's a matter of pushing many different breaks and accelerators to varying degrees in many different parts of a system: the system can be in several different states, none of them "blank" but not all of them "conscious" either. And some of them maybe even between a state of "conscious" and "unconscious" (like dreaming).
  6. Aug 3, 2012 #5
    It means to block sensation, not block consciousness.
  7. Aug 3, 2012 #6


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    Gold Member

    In the context of an anesthesiologist, it means consciousness. It also gets used for numbing agents ("local anesthetic") but that's not something you do to the brain, or need to be an anesthesiologist to do.

    Anyway, it's a jusfiable definition in the context. Also, Try googling "define: anesthetize".
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