|Neuroscience 1a – Development of the Nervous System
Review the development of the neural tube from the neurectoderm, and give an example of a clinical condition which results from abnormal development.
Explain what is meant by the neural crest cells, and give examples of their developmental fates.
Briefly describe how a simple tubular structure (the early neural tube) can give rise to the shape of the mature brain through differential growth and flexures.
Outline the cellular basis of formation of the ependymal, grey matter (mantle layer) and white matter (marginal layer) regions of the spinal cord, and the separation of the grey matter into sensory (alar) and motor (basal) regions.
Briefly outline how the development of the brainstem diverges from that of the spinal cord.
Briefly outline how cortical layers form from the neuroepithelium.
Trilaminar stage – 3 layers
Ectoderm thickens up in midline and becomes neural plate
These fold to become neural folds
Fuse to become neural tube. CNS
Neural Crest PNS
Separates off and moves laterally.
Neuroepithelium of Neural Tube
- forms the cells of the CNS
Give rise to glial cells (astrocytes, oligodendrocytes)
NB. Microglia develop from the mesoderm as they are blood cells that develop
Neural Crest Cells
- cells found at the tips of the ridges of the neural groove and are isolated in neurulation. They migrate during development to form:
Sensory neurones of dorsal root ganglia and cranial ganglia
Postganglionic autonomic neurones (e.g. sympathetic chain).
Schwann cells of Peripheral Nervous system.
Non-neuronal derivatives e.g. melanocytes
Proliferation occurs at the walls of the neural tube. This involves several repeats of the cell cycle.
Differentiation occurs on the outer surface of the CNS. They become neuroblasts and glial cells.
The neural tube surrounds the neural canal which in turn forms the canal of the fully developed spinal cord
Neuroblasts are contained within the tube
The neuroblasts adjacent to the canal in the Ependymal layer divide and migrate outwards within the tube forming the mantle layer, where they differentiate into neurones and form the grey mater of the cord
These cells then send fibres/developing processes out peripherally forming the white layer of the cord = marginal layer
The neuroblasts in the primitive grey matter form 2 discrete populations – the alar and basal plates separated by a shallow groove called the sulcus limitans