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Post by Admiral Lithp on Oct 7, 2011 21:39:08 GMT -5
I recently found myself wondering: If the brain is deprived of oxygen, which parts die FIRST? Which ones die last? What is the reason for this?
Google has failed me in my quest for answers.
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Post by Shane for Wax on Oct 7, 2011 22:23:54 GMT -5
I'm told the parts that deal with motor function dies first, then slowly the rest of them. What order the rest of them go in I don't know.
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Post by Napoleon the Clown on Oct 8, 2011 3:06:42 GMT -5
Lithp, please stop attempting auto-erotic asphyxiation. It's safer that way. Real answer: It probably depends. Non-essential functions go first, I would think.
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Post by Old Viking on Oct 8, 2011 15:39:23 GMT -5
Ask a conservative.
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Post by Mlle Antéchrist on Oct 8, 2011 22:59:35 GMT -5
Good question. My completely uncorroborated hypothesis would be that blood is rerouted to areas which control basic primitive functions needed for survival, killing fine motor skills and higher reasoning first. Google isn't returning anything to help me verify this, though.
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Post by Shane for Wax on Oct 8, 2011 23:04:09 GMT -5
I know that as you start experiencing hypothermia your motor skills start getting worse first then critical thinking and onward. I would assume it's the same with cerebral death.
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Post by Admiral Lithp on Oct 11, 2011 18:38:05 GMT -5
But, something that occurs to me with hypothermia, it's affecting your extremities first, then directing blood flow away from the brain when the smooth muscles are no longer able to keep the blood vessels constricted.
I also don't know if any part of the brain is more resiliant than other parts. I would think it would be similar to what you might get if you came out of a coma, or nearly drowned.
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Post by MaybeNever on Oct 12, 2011 3:18:50 GMT -5
The autonomic functions are the brain's first priority, to the extent that it will protect them even while letting the actual autonomic systems, such as the heart and lungs, die. The reason for this favoritism is presumably obvious.
Beyond that, the brain does not die systemically, such as having the visual cortex wink out like a light bulb. What die are the individual neurons, and while at some point the loss becomes sufficiently critical to prevent cortical function at any level, before that point you will see varying patterns of damage across the brain. The nature of the pattern probably has something to do with the individual's brain structure, level of fitness (or hemoglobin saturation), whether CPR was performed, and many other things that tend to make it unpredictable at best.
Curiously, the period just after resuscitation poses as much danger as the period without oxygen, as reperfusion injuries result when the brain is flooded with newly-oxygenated blood. This causes inflammation and prevents the proper flow of blood to all parts of the brain, not entirely unlike a stroke. As a result, further brain damage can arise in the hours following resuscitation if precautions aren't taken.
Unfortunately, our knowledge of the brain is poor and our knowledge of the brain in the actual process of dying is poorer. Once the brain is dead it is very hard to assess how damaged it was, and non-human subjects tend to be terrible at self-reporting their sensations while dying.
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Post by Admiral Lithp on Oct 12, 2011 14:04:10 GMT -5
No. I don't know what you mean by "autonomic" & "actual autonomic." What's the difference? I did not think it did, but I imagined that the random death would establish a general pattern, resulting from the average durability of the neurons, the average distance from the Circle of Willis, etc. True. In fact, the brain seems to be remarkably varied, compared to other anatomical structures. Then I think we have only one solution.
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Post by MaybeNever on Oct 12, 2011 14:19:59 GMT -5
No. I don't know what you mean by "autonomic" & "actual autonomic." What's the difference? The terminology I used wasn't very clear - I meant that the brain will protect the structures within itself that regulate the heartbeat, respiration, etc., even over the heart or lungs that make those things possible. This is probably what I should have said in the first place. Obviously that's kind of a "damned if you do, damned if you don't" situation - whether the heart dies or the ability to use the heart dies, you're still shafted. But the heart is a lot easier to replace than the brain, so this works out okay I guess. Part of the problem is that even the Circle of Willis varies quite a lot between people, such that there is only a very general path that it might follow in any given individual's brain. Likewise, the area or areas of brain being used dictates how blood is distributed, which will in turn be a factor in the longevity of those cells. I could be wrong on this point, but I don't believe that neurons are significantly differentiated on the cellular level in a way that would confer extra resilience to one system or region over another. Possibly regional glial density would play a role in this, but that's another one of those things that appears to vary strongly between individuals. I suspect that this is consequent to the brain just being both more complex and much harder to study in a useful way than other systems. If we knew more, we might be able to suss out other patterns that would reduce the apparent variability. This was once - in some cases less than a hundred years ago - a preferred method for anatomical study. But you probably knew that already.
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Post by Admiral Lithp on Oct 12, 2011 14:24:46 GMT -5
You mean studying executed prisoners, or stealing dead bodies?
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Post by MaybeNever on Oct 12, 2011 14:54:53 GMT -5
Both. And in at least one semi-famous case, killing people off the street for study.
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Post by Admiral Lithp on Oct 16, 2011 22:45:54 GMT -5
I have a new question:
How are thoughts & memories stored, as a physical object?
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Post by Mlle Antéchrist on Oct 16, 2011 23:08:53 GMT -5
I can't remember And by that I mean connections between neurons.
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Post by Vene on Oct 16, 2011 23:36:19 GMT -5
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