A1  Neural Development

big ninja

Essential Idea:

Modification of neurons starts in the earliest stages of

embryogenesis and continues to the final years of life


  • The neural tube of embryonic chordates is formed by infolding of ectoderm followed by elongation of the tube
  • Neurons are initially produced by differentiation in the neural tube
  • Immature neurons migrate to a final location
  • 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
  • A developing neuron forms multiple synapses
  • Synapses that are not used do not persist
  • Neural pruning involves the loss of unused neurons
  • The plasticity of the nervous system allows it to change with experience


  • Incomplete closure of the embryonic neural tube can cause spina bifida
  • Events such as strokes may promote reorganisation of brain function


  • Annotation of a diagram of embryonic tissues in Xenopus, used as an animal model, during neurulation