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Development of the Nervous System: Overview. "It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life." Lewis Wolpert (1986). Gastrulation occurs during 3 rd week of gestationin humans. What is an “organizer?”. ~19 days.
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Development of the Nervous System: Overview
"It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life." Lewis Wolpert (1986) Gastrulation occurs during 3rd week of gestationin humans
~19 days ~23 days
Rules for the Birth of Cells in the CNS 1. Proliferation begins in cervical segments and proceeds rostrally and caudally from there. 2. Large neurons are born first. 3. Motoneurons are born before sensory neurons. 4. Interneurons last of neurons born. 5. Glia proliferate after neurons, with the exception of radial glia.
Ventricular layer = ependymal layer = proliferative zone birthplace of CNS cells Mantle layer = newly born, post-proliferative cells Marginal zone = axonal layer
somites weeks 3-4 weeks 5-6
Segmental/Genomic Models Conventional Model
cephalic flexure cervical flexure
http://www.med.unc.edu/embryo_images/unit-nervous/nerv_htms/nervtoc.htmhttp://www.med.unc.edu/embryo_images/unit-nervous/nerv_htms/nervtoc.htm Embyronic Images by System University of New South Wales Embryology Online http://php.med.unsw.edu.au/embryology/index.php?title=Main_Page
Scanning EM of Migrating Neurons http://www.rockefeller.edu/labheads/hatten/mechanism.html Thanks to Aron Workman for finding this video clip.
Regressive Events in the Development of the Nervous System synapse withdrawal axon retraction programmed cell death (apoptosis)
Animation of Neuronal Proliferation and Migration in the CNS http://www.sumanasinc.com/webcontent/animations/content/neuronal_development.html