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Morrgan

Nerve cells regenerate?

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I was taught that once past a certain point in your development, the number of your nerve cells is fixed and that they don't regenerate. If you lose any, they stay lost.

 

But recently I heard that this is not the case and that nerve cells do regenerate, at least partially. Needless to say, I'm a bit confused now. Perhaps it's just a certain type, or depends on the type of damage to them? Could someone please shed some light on this?

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Peripheral nerves can regenerate if the damge is not too bad. These axons can grow at about 1mm per month. It used to be thought that cells in the central nervous system don't regenerate, but evidence of cell division has been found in certain areas of the brain. However, the process is slow and comparitively rare as there is no nerve growth hormone in the CNS. This is adaptive as the CNS is completely encased in bone and significant growth would be fatal to the organism. For all practical purposes, you might still say that brain cells, once damaged will not heal. The damage done by severe strokes (for example) is permanent. However, that evidence of cell division in the CNS has been found does suggest an interesting avenue of research with an aim to healing stroke damage and other CNS trauma.

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Thanks for the quick replies and the links. This made things clearer. I'll check later if I can get the full articles at uni.

 

Perhaps this is a stupid question, but can smaller damage to the brain after mild strokes be repaired then? I'd assume that in that case it'd be by "rerouting the wires"? (I don't know the correct terminology here, but I hope you know what I mean.)

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Once an area of brain dies through stroke, even micro strokes, it tends not to regenerate. In small strokes however, the functions of the damaged areas are taken up more readily by proximal areas than the functions of larger areas of damage. Large strokes often damage more than one region (areas dedicated to particular functions), which makes it hard for other areas to compensate. However, even damage through minor strokes require lots of re-learning by the individual; re-learning to speak, to control fine limb movements etc. The brain is quite a marvel. All the areas surrounding the damaged region, that are not actually dead can re-learn other functions. The degree of recovery by stroke patients can be quite amazing, over time of course.

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Is that true of all damaged regions? My grandfather has recently suffered short term memory loss due to a series of minor strokes.

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Well, by recovery, I mean that people who suffer for example, speech impediment after stroke, can usually regain most, if not all of their ability to speak, with a lot of speech therapy, and depending on the severity of the damage. They have to re-learn from scratch as undamaged but related regions begin to take over the functions of speech. Memory is different however. It depends on the type of amnesia he has; retrograde or anterograde. If it's retrograde (the loss of old memories) then they will be gone. You can't re-learn a memory, though if it's the traces that are gone, rather than the memories themselves, some may re-surface, given the right stimuli. If it's anterograde (the inability to form new memories) then he might improve with time, but it will require his learning new techniques for remembering things by the use of deliberate strategies. Again, the degree to which this will happen depends on the severity and precice location of the damage.

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