Neuron Development

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•  Neurons are initially produced by differentiation in the neural tube

The neural tube contains multipotent neuronal stem cells which can differentiate to form the different types of nerve cells:

  • Neurons are specialised nerve cells that conduct messages – they can be sensory, motor or relay (interneurons)
  • Glial cells provide physical and nutritional support for the neurons – roughly 90% of nerve cells in the brain are glial cells

Neurons are produced by progenitor neuroblasts via a process known as neurogenesis

  • Most neurons survive for the lifetime of the individual and do not proliferate following embryogenesis (they are 'post-mitotic’)
  • Certain brain regions may be capable of adult neurogenesis, but most of the nervous system is incapable of regeneration

Neuron Production via Neurogenesis


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•  Immature neurons migrate to a final location

Immature neurons must migrate in order to adopt precise final positions that allow for the formation of neural circuitries

  • This migration process is critical for the development of brain and spinal architecture

Neural migration may occur via one of two distinct processes – glial guidance or somal translocation

  • Glial cells may provide a scaffolding network along which an immature neuron can be directed to its final location
  • Alternatively, the neuron may form an extension at the cell’s perimeter and then translocate its soma along this length

Mechanisms of Neural Migration

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•  An axon grows from each immature neuron in response to chemical stimuli

•  Some axons extend beyond the neural tube to reach other parts of the body

An immature neuron consists of a cell body (soma) containing a nucleus and cytoplasm

  • Axons and dendrites will grow from each immature neuron in response to chemical signals from surrounding cells
  • Some axons may be quite short (within the CNS) but others may extend to other parts of the body (within the PNS)

An axon has a growth cone at its tip that contains highly motile growth filaments called filipodia

  • Extension of these filipodia causes the expansion of the internal cytoskeleton within the growth cone – resulting in growth
  • The direction of this expansion is controlled by chemical stimuli released from surrounding cells
  • These cells may release chemoattractant signals (grow towards) or chemorepellant signals (grow away)
  • Using these molecular guidance signals, axon growth cones may navigate long distances to reach specific targets

Axon Guidance by Chemical Signals

axon guidance