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Neurogenesis - Anatomy & Physiology (view source)
Revision as of 15:39, 26 August 2008
, 15:39, 26 August 2008no edit summary
===Formation of Cell Layers===
===Formation of Cell Layers===
#The neural tube begins with the germinal layer which is a single cell layer thick. All cells have the capacity to undergo mitosis.
#Some cells then lose their ability to undergo mitosis. They detach from the germinal layer and move away from the lumen, to exist behind the germinal layer.
#*This produces new layers called the '''mantle and intermediate layer'''.
#*The germinal layer is now known as the '''ventricular layer'''.
#Cells of the intermediate layer differentiate into one of two cells:
#*Neurones - for conductance of nerve impluses.
#*Glia - for insulation of electrical signals. Form oligodendrocytes in the CNS, and schwann cells in the PNS.
#Glial cells surrounds the axons furthest away form the lumen of the neural tube. Because this part is myelinated, it appears ''white''. It is called the '''marginal layer'''.
#Axons closer to the lumen of the neural tube, which the glial cells do not surround appear ''grey''. This layer is called the '''intermediate layer'''.
#The ventricular layer persists, so that the spinal cord develops with these three layers.
#In the brain, futher layers are added to increase complexity. This is possible because in the anterior of the embryo, neuroblasts (cells of the ventricular layer) retain their ability to undergo mitosis after leaving the ventricular layer.
#*This difference is achieved by increased hydrostatic forces acting on the neuroblasts.