Sanes;
Development of the Nervous System |
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Sanes; Development of the Nervous System |
52 |
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Cerebral cortex is not a homogeneous structure, but rather has many distinct regions, each of which has
a dedicated function. |
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Sanes; Development of the Nervous System |
52 |
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Brodmann (1909) classified the cerebral cortex into approximately
50 distinct areas. |
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Sanes; Development of the Nervous System |
52 |
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Although all neocortex areas
have six layers, the relative number of cells in each layer and the size of
the layer are quite variable and specialized for the specific function.
Visual cortex, a primary sensory area, has many cells in the layer IV the input
layer, whereas the motor cortex has very large neurons in layer V, the output
layer. |
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Sanes; Development of the Nervous System |
55 |
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One particularly
well-conserved class of transcription
factors, the Hox genes, is important in establishing and maintaining the regional identity of cells and
tissues along the anterior
posterior axis of vertebrates
throughout the hindbrain
and spinal cord. |
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Sanes; Development of the Nervous System |
59 |
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Cells of the ventricular
zone are the precursors of the differentiated neurons and glia of a central nervous system. |
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Sanes; Development of the Nervous System |
59 |
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Cells of the ventricular zone undergo from one to two cell cycles per day. |
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Sanes; Development of the Nervous System |
59 |
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In the early neural tube, many of the cells undergo
symmetric cell divisions, producing two progenitor cells as daughters. However some of the divisions produce asymmetric daughters: one daughter continues to divide, and the other becomes a post mitotic neuron. |
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Sanes; Development of the Nervous System |
59 |
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In the spinal
cord and in most other areas of the developing neural tube, the postmitotic neurons migrate from the ventricular zone to the marginal zone, where they continue
their differentiation. |
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Sanes; Development of the Nervous System |
72 |
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Newly generated neurons migrate from the ventricular zone into the cortical plate; they settle in progressively
more peripheral zones. |
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Sanes; Development of the Nervous System |
72 |
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Later
generated neurons migrate past those generated earlier. |
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Sanes; Development of the Nervous System |
72 |
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Inside-out development of cortical layers. |
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Sanes; Development of the Nervous System |
73 |
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Inside out pattern of cortical neurogenesis is conserved across mammalian species. |
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Sanes; Development of the Nervous System |
73 |
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Crawling of the neuroblast along the radial
glial scaffold. |
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Sanes; Development of the Nervous System |
85 |
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Progenitor cells from the early embryonic nervous system undergo many symmetric
cell divisions to make more progenitor cells, while the progenitor cells in the late embryo are more likely to undergo asymmetric division to generate neurons and glia. |
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Sanes; Development of the Nervous System |
85 |
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Once the developmental
period of neurogenesis is
complete, most areas of the brain do not generate new
neurons, even after damage. |
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Sanes; Development of the Nervous System |
85 |
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Certain regions of the brain, the hippocampus and the olfactory bulb, continue to add
new neurons throughout life. |
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Sanes; Development of the Nervous System |
85 |
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Continual addition
of neurons in regions such as the hippocampus and olfactory bulb may allow for greater plasticity in these specific brain circuits. |
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Sanes; Development of the Nervous System |
87 |
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Neurons show enormous variety in cellular anatomy, physiological function, neural chemistry, and conductivity. |
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Sanes; Development of the Nervous System |
87 |
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Motor neurons
of the spinal cord share a common morphology, chemistry,
physiology, and circuitry, yet they are distinctly specified
molecularly so that they
can connect with particular presynaptic partners and postsynaptic muscles. |
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Sanes; Development of the Nervous System |
111 |
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Some neurons, local
interneurons, have short
axons and make connections to cells in their immediate vicinity, while others, projection neurons, send their axons to distant targets. |
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Sanes; Development of the Nervous System |
111 |
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Sensory neurons from the periphery send axons into the CNS where they usually diverge to project to several distinct targets. Each of these targets
contains neurons that also diverge to various targets of their own, and so
on. |
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Sanes; Development of the Nervous System |
111 |
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Tracing backwards on the motor
side, each motor neuron is innervated
by many presynaptic neurons,
and each of these has its own multitude of inputs. |
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Sanes; Development of the Nervous System |
111 |
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Pioneer axons navigate in a simpler environment. As the brain
matures, more axons are added, and the weave becomes more intricate. As later axons navigate, they are aided by pathways laid down by earlier axons. Rich tapestry of the brain wiring is accomplished by successive addition of new fibers that add complexity in a stepwise fashion. |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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Sanes; Development of the Nervous System |
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