Neurons & Cell Repair: Understanding the Repair Process

[blackbird3]

I'm confused about the ability of neurons to repair themselves.

My understanding was that most tissue was repaired not by 'mending' individual cells but by creating new cells by cell division (and that most types of neurons don't actually do this) and that cells just became more worn until they die.

However, I've recently read an article which said that alcohol does not destroy neurons but it can damage dentrites - BUT the dendrites can later be repaired. If individual cells can repair parts of themselves in this way, does this mean that they are constantly replacing their materials e.g. replacing molecules in the cell walls as they get worn etc, or is there just a particular mechanism for mending dendrites? Do other types of cells have ways of repairing themselves and adding new molecules?

 

[BillTre]

Some neurons can repair themselves, such as regrowing cut axons, or perhaps dendrites as you mentioned.
If this is done, the stump of the axon (or the dendrite) will often develop a growth cone, a motile part of the cell that samples its local environment (often with filopedia, long thin branches or lammelopodia, little sheet-like extensions) to determine which way the fiber will extend.
This is like reinacting parts of the cells developmental program which generated its structure originally.

Not all cells, however, can do this. This could be due to the different properties of the differentiated neurons themselves or the environment of the neuron where the damage occurred (such as a cut peripheral nerve).
Some special neurons in particular invertebrates can be cut off from their cell bodies but remain alive and functional for long periods of time. This is due to metabolic support provided those cells from the invertebrate equivalent of glial cells.

Neurons are usually considered terminally differentiated, such that they will never again divide. Neurons are ot normally generated by other neurons but by neuroblasts (dividing neuronal precursors).
In the human brain there are a few areas that have been shown to have continued cell division, but more widespread adult neurogenesis is controversial. In other animals, post-embryonic neurogenesis occurs in several different cases (insects that go through metamorphosis is a good example).
Now that stem cells are being induced from a variety of cell types, it might be possible to get neurons to start dividing, but I am not aware of this.