Human Brain Development *Neural Tube Formation *Brain Growth *Synapse Formation By Cheryl Wilson, Belmont High School http://en.wikipedia.org/wiki/Brain_development http://commons.wikimedia.org/wiki/File:Brain_090407.jpg http://commons.wikimedia.org/wiki/File:Neuron_with_mHtt_inclusion.jpg

Neural Tube Formation- 2. Brain Formation- induction, proliferation & shape changes 2. Brain Formation- Proliferation, differentiation & migration http://commons.wikimedia.org/wiki/File:Gray16.png http://en.wikipedia.org/wiki/Brain_development http://en.wikipedia.org/wiki/Brain_development Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. http://commons.wikimedia.org/wiki/File:Fetus.jpg

3. Wiring the Brain & Nervous System Each neuron, once in place, must send axon connections to exactly the correct target! Gray matter-neuronal cell bodies (brownish when fixed) White matter-neuronal axon (connections) Some neurons have axons 3 feet long!!! Finding the proper target to make a connection with is a highly complex process! http://upload.wikimedia.org/wikipedia/commons/b/ba/Nervous_system_diagram.png http://commons.wikimedia.org/wiki/File:Visible_Human_head_slice.jpg Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

Growth, differentiation, development and normal functioning of the nervous system (like all organ systems) requires: Correct Gene Expression at the Correct Time and Place. http://commons.wikimedia.org/wiki/File:Complete_neuron_cell_diagram_en.svg

Neural Tube Formation in the Human Embryo-Cross Section Skin Body Cavity Neural Tube Neural Crest Central Canal Ectoderm Mesoderm Endoderm Neural Plate Neural Fold Notochord & Somites Neural Groove Neural Crest Neural Tube Early Neural Crest Neural Tube Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

Longitutinal Cross Section of Early Embryo Cephalic End Neural Tube (neurons and glia) Central Canal (will be spinal canal and ventricles) Caudal End Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. http://en.wikipedia.org/wiki/Brain_development

The 3-Vesicle Stage of Embryonic Brain Development http://commons.wikimedia.org/wiki/File:Encephalon.png and edited by CW http://commons.wikimedia.org/wiki/File:4_week_embryo_brain.jpg Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

The 5-Vesicle Stage of Embryonic Brain Development Metencephalon Mylencephalon http://commons.wikimedia.org/wiki/File:6_week_embryo_brain.jpg http://commons.wikimedia.org/wiki/File:Encephalon.png and edited by CW Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

Overview of Brain Development 1. Neural Tube Formation 2. Brain Formation 3. Wiring the Brain & Nervous System http://upload.wikimedia.org/wikipedia/en/1/1b/Development_of_nervous_system.png and edited by CW http://commons.wikimedia.org/wiki/File:4_week_embryo_brain.jpg http://commons.wikimedia.org/wiki/File:6_week_embryo_brain.jpg http://commons.wikimedia.org/wiki/File:Brain_bulbar_region.svg http://en.wikipedia.org/wiki/Brain_development Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

Longitutinal Cross Section of Early Embryo Cut Cephalic End Neural Tube Cross-Section Neural Tube (neurons and glia) Central Canal (will be spinal canal and ventricles) Caudal End Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. http://en.wikipedia.org/wiki/Brain_development

Inside Out Brain Growth in the Human Embryo- Neurons proliferate on the ventricular side of the neural tube Neurons migrate towards the marginal side in waves Each wave of neurons travel past the earlier layers Again. Neural Tube (early CNS) Central Canal (early spinal cord or brain ventricles) Ventricular zone (inner) Most neurons migrate radially from the ventricular zone towards the marginal zone, following glial cell fibers. Again. Marginal zone (outer) The next wave of migrating neurons goes past the previously-settled cells. Again. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

Correct temporal-spatial gene expression is critical for the correct neurons to find each other! 3. Once neurons have reached their final destination, they must now send out their axons to make connections with the correct target and be responsive to receive the correct signals. 2. Cells migrate past the last wave of cells to deposit 1. Ventricular zone- Where proliferation/cell division occurs http://en.wikipedia.org/wiki/Brain_development With labelling by CW Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

http://commons.wikimedia.org/wiki/File:Gray754.png Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.