8 week: Changing brain
This week we discovered a lot about changing brain. From my perspective, it is very interesting to understand how the brain actually develops. Mature cortical cells can be classified as glia or neurons, and the neurons can be further classified according to the layer in which they reside. There are 5 different layers and the position or the fate of the daughter cells depends on the plane of cleavage during division. Also, cells can migrate. The daughter cells follow the path from the ventricular zone toward the surface of the brain. Interestingly, each new wave of cell migration past those in the existing cortical plate, meaning that the cortex is to be assembled “inside out”. After that, the differentiation of neuronal cells takes place, for example, layer V and VI neurons have differentiated into the pyramidal cells.
After the cells are differentiated, there is one more important step left – reaching the appropriate target by axonal growing. This process is quite complicated, because not only the target needs to be found, but also the right path to this target and the right layer within the target. Also, I heard from childhood that once the neurons are degenerated it will not develop again, and now I read about it deeply and I can say that in the adult mammalian CNS this growth is aborted, but not in the mammalian PNS. PNS axons are capable of regeneration.