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Search the siteDevelopment of the human nervous system
7th June 2019
The nervous system begins being generated around at around the 20th day of embryogenesis.
In a process called neurulation, the first form of the system, referred to as the
neural plate, emerges from the ectoderm of the gastrula.
At around the 3rd or 4th week, the neural plate transforms
into the neural tube. The neural tube’s cells are still undifferentiated and capable of turning
into any kind of neural or glial cell. Eventually, the neural tube will form the brain and the
spinal cord. Until the late stage of the human embryo, the nervous system will have formed
nearly all of its neuronal cells – with the few exceptions of the new neuronal cells that will
form by neurogenesis throughout the human’s life. As the infant grows, the neurons that are
functional will stay alive, while the rest will atrophy and disappear (sometimes this process is
called “pruning”). This is why this period (up to around 7 years of age) of a human’s life is said
to be a “critical stage” for leaning.
The neural tube first shows three distinguishable components, called the forebrain, the midbrain and the hindbrain. The nervous system at this stage is growing in a head-to-tail direction, like shown in the image below:
The undifferentiated precursor neural cells (called neuroblasts) travel to their destination (on the brain or spinal cord) and then differentiate into their cell type – their differentiation depends on transcription factors that turn the appropriate genes on or off.
Once neuronal cells are formed, they start growing axons, which, guided by molecular clues, seek out their target cells, which could be either neuronal, muscular, or gland cells. Once they find their target cells, the axon endings begin forming synapses; a process called synaptogenesis. While the required synapses will be developing, those that prove unnecessary will break down or rearrange into new synapses.
On the other hand, the different types of glial cells also form. One type, called oligodendrocytes, will begin to form myelin in a process called myelination.
The neural tube first shows three distinguishable components, called the forebrain, the midbrain and the hindbrain. The nervous system at this stage is growing in a head-to-tail direction, like shown in the image below:
The undifferentiated precursor neural cells (called neuroblasts) travel to their destination (on the brain or spinal cord) and then differentiate into their cell type – their differentiation depends on transcription factors that turn the appropriate genes on or off.
Once neuronal cells are formed, they start growing axons, which, guided by molecular clues, seek out their target cells, which could be either neuronal, muscular, or gland cells. Once they find their target cells, the axon endings begin forming synapses; a process called synaptogenesis. While the required synapses will be developing, those that prove unnecessary will break down or rearrange into new synapses.
On the other hand, the different types of glial cells also form. One type, called oligodendrocytes, will begin to form myelin in a process called myelination.
