Neural development
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The study of neural development draws on both neuroscience and developmental biology to describe the cellular and molecular mechanisms by which complex nervous systems emerge during embryonic development and throughout life.
In a study conducted by Oxford University, on January 11th 2007, found that in comparison of 8 adult and newborn brains, that the newborns had almost double (11.6 million) the amount of neurons than in adults (6.43 million), whereas counts in glial cells in adults (32 million), showed almost triple the number of those in children (10.3 million). [1]
Some landmarks of embryonic neural development include the birth and differentiation of neurons from stem cell precursors, the migration of immature neurons from their birthplaces in the embryo to their final positions, outgrowth of axons from neurons and guidance of the motile growth cone through the embryo towards postsynaptic partners, the generation of synapses between these axons and their postsynaptic partners, and finally the lifelong changes in synapses which are thought to underlie learning and memory.
Typically, these neurodevelopmental processes can be broadly divided into two classes: activity-independent mechanisms and activity-dependent mechanisms. Activity-independent mechanisms are generally believed to occur as hardwired processes determined by genetic programs played out within individual neurons. These include differentiation, migration and axon guidance to their initial target areas. These processes are thought of as being independent of neural activity and sensory experience. Once axons reach their target areas, activity-dependent mechanisms come into play. Neural activity and sensory experience will mediate formation of new synapses, as well as synaptic plasticity, which will be responsible for refinement of the nascent neural circuits.
Developmental neuroscience uses a variety of animal models including the fruit fly Drosophila melanogaster , the zebrafish Danio rerio, Xenopus laevis tadpoles and the worm Caenorhabditis elegans, among others.
Contents |
[edit] First stage: Neurulation
- Main article: neurulation
- See embryogenesis for understanding the animal development up to this stage.
Neurulation follows gastrulation in all vertebrates. During gastrulation cells migrate to the interior of embryo, forming three germ layers (endoderm, mesoderm and ectoderm) from which all tissues and organs will arise. In a simplified way, it can be said that the ectoderm gives rise to skin and nervous system, the endoderm to the guts and the mesoderm to the rest of the organs.
After gastrulation the notochord - a flexible, rod-shaped body that runs along the antero-posterior axis - has been formed (derived from mesoderm). The notochord sends signals to the overlying ectoderm, inducing it to become neuroectoderm, composed of neuronal precursor (or stem) cells. This is evidenced by a thickening of the ectoderm above the notochord, the neural plate. The neural plate will form the neural tube which then twists, turns and kinks to form the three primary brain vesicles and five secondary brain vesicles. The end result of this process is described in the article on the regions of the brain.
[edit] Human brain development
[edit] See also
- Animal development
- Nerve growth factor
- Neural Darwinism
- Neural development in humans
- Neural plasticity
- Neural regeneration
- Neural transplantation
- Reinnervation
[edit] External links
- Myers, P.Z., 2004. "Neurulation in Zebrafish" in Pharyngula [1].
| This page uses content from the English-language version of Wikipedia. The original article was at Neural development. The list of authors can be seen in the page history. As with Psychology Wiki, the text of Wikipedia is available under the GNU Free Documentation License. |
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