Answer
In adults neurogenesis does not take place in most parts of the brain--the hippocampus is an exception This is not the case in the peripheral nervous system where nerve damage is often repaired , albeit very slowly
Work Step by Step
Factors that militate against CNS neurogenesis are the following:
In the CNS, myelination is accomplished by oligodendrocytes. In contrast, PNS myelination is carried out by Schawnn cells. Oligodendrocyte myelination inhibits neurogenesis. Also, adult CNS tissue lacks growth stimulatory factors/cues present during embryonic development. In addition, after nerve damage, astrocytes of the CNS rapidly form scar tissue that blocks the path of new tissue growth.
