MadSci Network: Neuroscience
Query:

Re: What exactly is neurogenesis ?

Date: Fri Dec 17 14:09:35 1999
Posted By: James Goss, Post-doc/Fellow, Neurology, University of Pittsburgh
Area of science: Neuroscience
ID: 942333333.Ns
Message:

Neurogenesis is a term that refers to the process of making neurons.  
During embryogenesis, certain areas of the developing embryo, called the 
neuroectoderm will eventually become the nervous system.  I don't have the 
space to describe all that is known to be involved in process and suggest 
that you refer to a basic neuroscience textbook.  Probably the major 
question in developmental biology deals with the process of 
differentiation.  In an adult, the cells that make up the various organs 
and structures have distinct characteristics - you can tell a liver cell 
from a muscle cell from a neuron.  But there is a time during embryogenesis 
when this is not the case and an embryonic cell can become one of several 
types of cells (we often call these type of cells pleurypotent cells, 
precursor cells, or stem cells).   These stem cells differentiate into 
specific types of cells (like liver cells or neurons) due to several 
different factors including what genes are turned on in them, proximity to 
other cells, and their extracellular environment.  The precursor cells to 
neurons are called neuroblasts.  The differentiation of neuroblasts into 
neurons is neurogenesis.  Neurogenesis is also used to describe the 
formation of the various structures of the nervous system, for example the 
neocortex or the cerebellum.  The nervous system is highly complex, very 
structured, and made up of many different types of neurons and non-neuronal 
cells.  Each cell must end up in the proper place and perform the correct 
function if the nervous system is to work properly.  
   Until recently, it was thought that there was no neurogenesis in the 
adult brain.  It was thought that you were born with the entire complement 
of neurons you would ever have because neurons are 'terminally 
differentiated', that is, they do not divide once they become neurons.  
However, recent experimental evidence suggests that this is not necessarily 
the case and that neuronal precursor cells can still be found in the adult 
brain.
   I hope this helped to answer your question.



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