Essential Idea:
Modification of neurons starts in the earliest stages of
embryogenesis and continues to the final years of life
Understandings:
- 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
Applications:
- Incomplete closure of the embryonic neural tube can cause spina bifida
- Events such as strokes may promote reorganisation of brain function
Skills:
- Annotation of a diagram of embryonic tissues in Xenopus, used as an animal model, during neurulation