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Myelin is formed by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system.Therefore, the first stage of myelinogenesis is often defined as the differentiation of oligodendrocyte progenitor cells (OPCs) or Schwann cell progenitors into their mature counterparts, [4] followed by myelin formation around axons.
The process of generating myelin is called myelination or myelinogenesis. In the CNS, oligodendrocyte progenitor cells (OPCs) differentiate into mature oligodendrocytes, which form myelin. In humans, myelination begins early in the 3rd trimester, [ 11 ] although only little myelin is present in either the CNS or the PNS at the time of birth.
Beginning in the future neck region, the neural folds of this groove close to create the neural tube. The formation of the neural tube from the ectoderm is called neurulation. The ventral part of the neural tube is called the basal plate; the dorsal part is called the alar plate. The hollow interior is called the neural canal. By the end of the ...
The remainder of the ectoderm gives rise to the epidermis. The ability of the mesoderm to convert the overlying ectoderm into neural tissue is called neural induction. In the early embryo, the neural plate folds outwards to form the neural groove. Beginning in the future neck region, the neural folds of this groove close to create the neural tube.
The maturation of myelination in intracortical layers coincides with critical period closure in mice, which has led to further research on the role of myelination on critical period duration. [ 37 ] Myelin is known to bind many different axonal growth inhibitors that prevent plasticity seen in critical periods. [ 38 ]
Different portions of the neural tube form by two different processes, called primary and secondary neurulation, in different species. [4] In primary neurulation, the neural plate creases inward until the edges come in contact and fuse. In secondary neurulation, the tube forms by hollowing out of the interior of a solid precursor.
Q3 can be particularly important to some seasonal businesses, as on a calendar-year basis, Q3 represents the end of summer holidays and the return to the school year.
RGCs are the primary stem cells of the mammalian CNS, and reside in the embryonic ventricular zone, which lies adjacent to the central fluid-filled cavity (ventricular system) of the neural tube. [ 5 ] [ 6 ] Following RGC proliferation, neurogenesis involves a final cell division of the parent RGC, which produces one of two possible outcomes.