Brain Plasticity: Neurodevelopment
- Created by: meg_lou
- Created on: 20-04-17 09:29
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- Neurodevelopment
- Phases
- Induction of the neural plate
- 3 weeks after conception, tissue becomes the neural plate
- Small patch of ectodermal tissue on dorsal surface of embryo
- Ectoderm is the outermost layer of embryonic cells
- Induced by chemical signals from the mesoderm (middle layer)
- Small patch of ectodermal tissue on dorsal surface of embryo
- Cells of the neural plate are called embryonic stem cells
- Unlimited capacity for self-renewal if in right conditions
- Pluripotent - capable of developing into any kind of cell
- Neural plate develops into the neural tube
- 3 weeks after conception, tissue becomes the neural plate
- Neural proliferation
- Does not occur simultaneously or equally in all parts of the tube
- Most cells divide in the ventricular zone, adjacent to the ventricle (centre of tube)
- Does not occur simultaneously or equally in all parts of the tube
- Migration and aggregation
- Radial migration - from ventricular zone straight to outer wall of tube
- Tangential migration - parallell to the tube's walls
- Aggregation - neurons must align themselves with other neurons that have migrated to the same area and form structures of the NS
- Tangential migration - parallell to the tube's walls
- Neural crest dorsal to the neural tube and formed from neural tube cells
- Develops into the cells from the PNS and they migrate long distance
- Radial migration - from ventricular zone straight to outer wall of tube
- Axon growth and synapse formation
- Axons and dendrites begin to grow
- Growth cones, at the growing tips of axons, extend and retract cytoplasmic extensions called filopodia
- Chemoaffinity hypothesis - post synaptic targets release a chemical that guides axonal growth
- Although some growing axons follow the same circuitous route to reach a target
- Synapse formation relies on glial cells
- Glial cells provide extra cholesterol which is needed
- Also process, transfer and store information supplied by neurons
- Glial cells provide extra cholesterol which is needed
- Axons and dendrites begin to grow
- Neuron death and synapse rearrangement
- 50% more neurons than needed are produced
- Neurons die due to failure to compete for chemicals provided by targets
- Destroying more cells (apoptosis) increases survival rate of remaining ones
- As neurons die there is space vacant where axon terminals grow so there is synapse rearrangement
- 50% more neurons than needed are produced
- Induction of the neural plate
- Postnatal growth
- Increase in size
- The volume quadruples between birth and adulthood
- Not a result of additional neurons
- The volume quadruples between birth and adulthood
- Visual deprivation
- Fewer synapses and dendritic spines in primary visual cortex
- Deficits in depth and pattern vision
- Fewer synapses and dendritic spines in primary visual cortex
- Increase in size
- Brain plasticity in adults
- Developmentof new neurons occurs in variety of brain regions
- E.g. stem cells differentiate into new neurons in hippocampusto facilitate learning
- Skills training
- Changes the brain in a way that improves the ability for that skill
- E.g. temporal lobe of professional musicians is 30% larger than non-musicians
- Reorganisation of the brain can go too far
- Fingers of musicians who practice extensively become clumsy and tired easily
- Arises from extensive reorganisation of the sensory thalamus and cortex
- Fingers of musicians who practice extensively become clumsy and tired easily
- Changes the brain in a way that improves the ability for that skill
- Developmentof new neurons occurs in variety of brain regions
- Development
- Brain has neural elements wired to have a network of circuits
- Starts with a single fertilised egg then ends with a functional adult brain
- Once thought that new neurons were not formed after initial development
- Stem cells can produce daughter cells that transform into glia or neurons
- New olfactory receptors continuously replace dying ones
- Brain has neural elements wired to have a network of circuits
- Phases
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