Central Nervous System Development : Neural Induction, Neurogenesis, Migration, Axon Guidance, And Synaptic Development

In the neural tube, neuroepithelial cells line the ventricular wall, are densely packed, and form the ventricular zone. They will eventually divide and form radial cells which act as stem cells and provide scaffolding. While continuing to migrate, migrating cells then differentiate into neurons and glia. The development of the brain can now be considered, from a cellular viewpoint, as a sequence of six different stages, most of which happen during prenatal life. We first start off with phase 1, neurogenesis, which is the mitotic division of nonneuronal cells to produce neurons, phase 2, cell migration, is the massive movements of nerve cells or their precursors to distinct areas of the nervous system. The 3rd phase is cell differentiation, the changing of cells into distinct types of neurons or glial cells. Then we have the 4th stage of synaptogenesis, the formation of synaptic connections, which are equal to small gaps through which nervous system cells communicate to one

Beginning at four weeks, the neurons begin to develop, 500 thousand per minute. The neurons begin to build the brain, by making layers. The video uses the example of an onion being built in layers. Neurons are the only cells that have to move along in a “migration” path to form the brain. Scientists have found that the neurons know where they are migrating to, and

The process of myelination is pivotal in the development of young children. The myelin is a fatty coating surrounding the axon that increases transmission between neurons. Before the age of six they are maturing and developing faster whereas, under six the child may forget what they are doing before they finish the task at hand. At six years old the most children can see an object and identify it, catch and throw a ball, and write their ABC sequences without default. Information is still processing slowly at six years of age (Berger, 2011).

inhibitory signals from the glia and the extracellular environment and forms scars rapidly. Not much

1) the regulation of modes of division that are essential to control brain grow and neuronal differentiation; disruption of proliferative and asymmetric mode of divisions is believed to be at the origin of microcephalies and cancers in humans.

The development of the cortex is a delicate balance between proliferation, differentiation and migration of neural progenitors (NPs). Throughout developmental process, various cellular mechanisms ensure that NPs are differentiating into the correct cell subtypes, migrating to their correct regions, and forming the correct cortical and sub-cortical layers. The cortex is comprised of both excitatory and inhibitory neurons, which interact within neuronal circuits to mediate cortical functions. Though both types of neurons reside in the cortex, they arise from different embryonic brain regions, and from different neural progenitors. Excitatory neurons are generated from neural progenitors residing in the ventricular zone (VZ)/subventricular

Precise control over the routes taken by growing neurons is tightly controlled (Steward, 1989). In the brain extracellular cues play an important part prompting attractive or repulsive behaviours in cell migration. In addition, they are necessary for cell adhesion, axon guidance and branching (Erskine & Herrera, 2007). For neurons that navigate over long distances, axons can be guided by chemoattractants that draw axonal navigation in its direction or chemorepellents that deter axonal growth in its region.

Neuronal multiplication, differentiation, and migration are occurring by the third week of embryonic life. Germinal cells proliferate in the matrix layer adjacent to the neuroaxis lumen and undergo transformation into neuroblasts which periodically migrate with great predictability to the marginal layer, which will later becomes the cortex. Migration is completed near the fifth fetal month and mitotic figures disappear by the end of the sixth fetal month. Thus by twenty-four weeks, the embryo has its full quota of neuronal mass. Further gross brain development continues to birth with the enfolding of the surface to form sulci and gyri and this predictable pattern is a reliable estimate of fetal age. Definitive cytoarchitectural patterns are evidenced at birth, which are the products of myelination having occurred at various levels at specific times, as well as the growth of glial cells. Visual tracts become myelinated soon after birth, and the corticospinal tracts continue to myelinate into the second year of postnatal life, after which time most myelination of the cerebrum is becoming complete.

Article assignment: Here is the link to an interesting review article on neurogenesis. Please read the article and briefly answer each of the questions. Upload the document to DROPBOX by the due date. You may not understand all of the terms, but try and get the basics!

Cnidarians do not have a central nervous system (no local concentration of nerve cells, no brain), but the anemones simple differentiated nervous system works much the same. Arrangements of nerve cells within a loose network called nerve nets process and respond to stimuli much like a brain would. For example, in response to stimuli, nerve cells emit electrical impulses through the nerve net to all parts of the anemone’s body, causing contractions in the anemone’s muscles. The result is movement.

Central nervous system (CNS) is composed of brain and the spinal cord. Neurons constitute a major part of the developing CNS. An axon is an extension of a neuron. The brain grows as a swelling at the front (rostal) end of the neural tube and later leads to become a spinal cord (1,2). Development of the CNS involves many complex mechanisms beginning at the onset of transformation of a single layer of ectodermal cells, the neuroectoderm until the end of the differentiation process resulting into highly complex structure involving variety of neural cell types (1,2). A large number of cell types need to be arranged spatially and temporally to form a complex structure during an

In the past, people thought children’s brains only developed through genetics, but as the years passed, this theory has been proven wrong. People discovered that it was more than genetics. Genes and developing environmental connections are important, but play different roles. Genetics provide neurons and cells, connecting those to different parts of the brain, whereas, environmental connections use the neurons to strengthen the neurons to shape the individual. Moreover, without each other these connections wouldn’t be developed and genetics would weaken. The connections babies make in their environment increase brain activation and development plays a significate role in children’s lives. In

Neurons themselves cannot split and divide to create more neurons. But like other stem cells, neural stem cells have the ability to split and divide themselves indefinitely to further create more neural stem cells, or to differentiate and become Progenitor cells. Progenitor cells are early stage cells and can be of different types like Neural or Glial. The Progenitor cells can either decide to stay neural stem cells or they themselves differentiate to form either neurons or support cells. In the case of Neurogenesis, the Neural Progenitor cells mature to form new

Synaptic connections are signals that allow neurons (nerve cells) to connect and pass from one to the other, within the cerebral cortex of the brain. It allows the baby to develop color vision, pincer grasp, or a strong attachments with parents.

Human brain development represents a dynamic and complex process that requires fine tuning of biochemical, genetic, environmental and physical events. Neuronal migration is a significant part of neurodevelopment, which is a term that describes moving of nerve cells from their origin to their ultimate location.