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This question could be considered a follow-up question to Why is a lack of oxygen fatal to cells?, although the top answer there does not address why damage starts to pop in.

The answer says this:

Neurons are also highly metabolically active, which means they generate more waste products. A buildup of nitrogenous waste products in the cell (and bloodstream) can be potentially fatal due to it's effects on pH (screws up enzymes and a whole slew of biochemical reactions)

But when the brain is deprived of oxygen, metabolism shuts down. So waste products aren't being generated anymore.

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Basically I'm wondering - what causes neurons, in particular, to die so quickly (relative to other cells, like kidney cells) after they're depleted of energy?

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who said anything about metabolism shutting down when the brain is deprived of oxygen? Brain cells die, sure, is that what you mean by "shut down"? Are you implying that they go into some kind of dormant state before they die? –  Shep May 6 '12 at 16:03
    
Doesn't metabolism shut down before death occurs? Or does the metabolism start causing damage, which causes death in the process? –  InquilineKea May 6 '12 at 17:16
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this isn't very scientific, but metabolism shutting down is death in some sense. Our neurons aren't designed to be shut down, so if that happens they start to fall apart (die). –  Shep May 6 '12 at 17:23
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FYI: I've opened a related question on how much our brains' metabolic rate varies. My guess is that since neurons consistently use lots of energy, they are totally unprepared to exist in a low-metabolism state. –  Shep May 6 '12 at 19:37
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But on the other hand, some organisms can be frozen and revived. In that case, metabolism is shut down but death does not occur. –  InquilineKea May 6 '12 at 21:08

1 Answer 1

There is a good review in the Journal of Experimental Biology (Bickler and Donohoe 2002, JEB 205, 3579–3585) I will just summarize for those that do not have access to the review.

Neurons use lot of energy to maintain their polarized state, this is not required to other cells. When O2 or blood flow is reduced, the neuronal ATP levels breaks down very fast, with 90% ATP depleted in less than 5 minutes. Without ATP, the neuron can not maintain the correct ion flux, so depolarization occurs causing glutamate excitotoxicity, cell swelling and finally cell death.

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+1. Neurons use a lot of active transport pumps that consume ATP to maintain ion gradients and to shuttle neurotransmitters. –  yamad May 9 '12 at 3:29

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