Neuroscience 1a Development of the Nervous System

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Neuroscience 1a – Development of the Nervous System

Anil Chopra

  1. Review the development of the neural tube from the neurectoderm, and give an example of a clinical condition which results from abnormal development.

  2. Explain what is meant by the neural crest cells, and give examples of their developmental fates.

  3. 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.

  4. 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.

  5. Briefly outline how the development of the brainstem diverges from that of the spinal cord.

  6. Briefly outline how cortical layers form from the neuroepithelium.

Early Development

  1. Trilaminar stage – 3 layers

    1. Ectoderm thickens up in midline and becomes neural plate

    2. These fold to become neural folds

    3. Fuse to become neural tube.  CNS

  2. Neural Crest  PNS

    1. Separates off and moves laterally.

Neuroepithelium of Neural Tube

- forms the cells of the CNS

  • Neuroblasts

  • Glioblast

    • Give rise to glial cells (astrocytes, oligodendrocytes)

    • NB. Microglia develop from the mesoderm as they are blood cells that develop

  • Ependymal Cells

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

Cellular Process
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
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