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Neural Development
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- 1NEURAL DEVELOPMENT Beginning - ECTODERM - outer layer becomes nervous system - neural groove forms between ridges of ectoderm Neural tube - forced from neural ridges Anterior part - 3 subdivision, forebrain, midbrain, hindbrain6 STAGES OF NEURAL DEVELOPMENT
1. NEUROGENESIS
- mitosis produces neutrons from non neuronal cells
- cells of neural tube = divide forming ventricular zone
- birth - most neutrons - post birth brain weight increases due to, myelination, dendrite branching, glia cells
- tiny % of neutrons acquired through adult neurogenesis - enriched experiences - exercise and learning - 22. CELL MIGRATION - - cells move to establish distinct population by migrating to appropriate regions - RADIAL glial cells act as guides - CELL ADHESION MOLECULES (CAMs) promote adhesion of parts of nervous system to guide cells - some cells remain ventricular zone - continue neurogenesis - some migrate to marginal zone3. DIFFERENTIATION -
- cells of cerebral cortex arrive in waves - each one forms new outer layer - 6 layers formed
- D = when cells reach destination begin to express genes to make proteins they need
- allows a cell to acquire specific appearance/function
- TWO TYPES OF INFLUENCE
- cell autonomous (organisation) - independent of others driven by genes, intrinsic organisation in vitro
- induction (neural environment) - affected by influence of other neighbouring cells - 3REGULATION - response to cell injury in development - other cells develop to take place STEM CELLS - undifferentiated divide - daughter cells can assume new cell fate4. SYNAPTOGENESIS -
- neurons extend axons and dendrites and form synapses with one another
PROCESS OUTGROWTH - extensions (filopodia) emerge from growth cones - tips of axons and dendrites
Filopodia adhere to CAMs and pull growth cone in particular direction
Axons - guided by chemical released by target cells
SYNAPTOGENESIS - synapses form rapidly on dendrites and dendritic spines
spines proliferate after birth and connections are affected by experience
Nerve cell body increases in volume to support dendritic tree - 45. NEURONAL CELL DEATH (APOPTOSIS) cells express death genes expressed ONLY during APOPTOSIS CAPSASES = proteases = cut up proteins and DNA destroy cell Ca2+ influx = mitochondria release diablo - binds to inhibitors of Apoptosis proteins (IAPs) which normally inhibit capsases without IAP inhibitors - capsases = dismantle cell - neurons compete for chemical target cells make6. SYNAPSE REARRANGEMENT -
synaptic pruning - refines synaptic connections
influence on synaptic survival = neural activity - 5BRAIN PLASTICITY - brain is plastic when young - injury to part of brain can allow function to develop in other brain areas AS WE AGE - plasticity slows down = becomes static