I am not a biologist - my background is in quantitative sciences, and I am trying to answer a rather quantitative question:
How much oxygen does a brain consume?

This however raises many sub-questions of purely biological nature:

  • How is the brain supplied by oxygen? (My naive understanding is that lungs tie oxygen to hamoglobin, which is then carried by blood to cells, which then ingest the oxygen, converting it to ATF. Is this correct? Does this apply to neurons as well?)
  • How much energy a neuron or the whole brain consumes per unit time? (e.g., per hour, in energy units or oxygen content)

I will appreciate explanations in laymen terms or references to accessible literature.

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    $\begingroup$ dentinstitute.com/posts/lifestyle-tips/… #16.please do a tiny bit of research before asking it here. $\endgroup$ Aug 31 '20 at 13:05
  • $\begingroup$ @trondhansen I've been doing research, and the link that you sent is a bit lightweight - e.g., it says nothing about blood-brain barrier. Also, I need to see the numbers - e.g., how much energy does brain consume in Joules or kcals per hour? $\endgroup$ Aug 31 '20 at 14:20

As has been commented, the answers to some of the questions here can be found in the literature. The nutrients and oxygen reach all tissues by the circulatory system — i.e. in the blood. And the link supplied by @trondhansen suggests a litre of oxygen a day. (I wouldn’t know — I never studied physiology.) However, as regards energy, I supply the following from the biochemistry text, Berg et al.

Brain. Glucose is virtually the sole fuel for the human brain, except during prolonged starvation. The brain lacks fuel stores and hence requires a continuous supply of glucose. It consumes about 120 g daily, which corresponds to an energy input of about 420 kcal (1760 kJ), accounting for some 60% of the utilization of glucose by the whole body in the resting state.

Note the correct form of expression:

the brain / consumes fuel / to generate energy / to perform ‘work’

Glucose is the fuel, ATP is the chemical energy currency, and the work performed (as the text makes clear) is for the main (60%–70%) to:

maintain the sodium/potassium ion membrane potential required for the transmission of the nerve impulses.

(I am afraid that’s about as layman’s terms as I do. It does say on the label that this site is for students of biology.)

  • $\begingroup$ Thank you for the explanations and for the reference (I have found a similar number - that brain consumes 20% of the total daily energy intake, which is about 2000 kcal.) Do I understand correctly that neurons receive both the sugars and the oxygen via the blood stream as raw materials, and convert them to ATP, just like any other type of cells? $\endgroup$ Sep 1 '20 at 9:10
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    $\begingroup$ Yes indeed. However cells are different in the way that the hormones of the fed and starved state affect the uptake of glucose through the cell membrane. This is done by transporter proteins. For tissues that can use other fuels in starvation, insulin is required by the transporters to prevent them using glucose, which is prioritized for the brain. The brain transporters are subtly different, in that they do not require glucose. The ATP generation is the same. $\endgroup$
    – David
    Sep 1 '20 at 9:14
  • $\begingroup$ The project that I am working on actually presupposes using liposomes as a method for delivery of extra (Hb-bound) oxygen to the brain. From what I read, the liposomes are necessary for overcoming BBB (blood-brain barrier) which is inpenetrable for most drug-delivery methods. But it seems that this also raises the question of supplying additional sugars... $\endgroup$ Sep 1 '20 at 9:23
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    $\begingroup$ I don’t really know. I would doubt you could or would need to do that. Glucose uptake is usually a pull method in response to demand. $\endgroup$
    – David
    Sep 1 '20 at 9:27

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