Lecture 11 Nervous System Development II Flashcards
What are the 8 stages of cortical development?
Martha carried Neurals along three stations: Proliferation, Migration & Differentiation. After leaving them at the final station, she met the Growth twins: Axonal & Dendritic. They had lunch at Synaptogenesis and went to Myelination arcade. While coming out, they saw an accident on Neuronal Death street.
- Neural Proliferation
- Neural Migration
- Neural Differentiation
- Axonal Growth
- Dendritic Growth
- Synaptogenesis
- Myelination
- Neuronal Death
Neural proliferation
Neural proliferation occurs after ________ , near fluid filled sacs which is made possible by the formation of the _____ & ______ because that is where ________ are for cells to grow.
Neural tube closure, lateral ganglionic eminence, medial ganglionic eminence, nutrients
Describe the event of neural proliferation
- occurs at high rate in ventricular zone
- A stem cell -> progenitor - go back to ventricular zone
-> neuroblast (differentiated) -> travel up radioglia to Cortex
Where are new cells born
Where do the cells actually live
Ventricular zone
Subventricular zone
Describe the layers of the neural tube from inside to outside (bottom to top) and what takes place there
Ventricular zone - neural proliferation
Subventricular zone - where stem cells live
Intermediate zone - radial glia process crosses it
Cortical plate - neuroblasts are laid down into their respective layes
Marginal zone - Cajal-retzius cells
Meninges
Cellular migration
What kind of cells migrate from the ventricular layer? What are characteristics for this cell?
Neuroblasts (non-dividing cells)
- immature structure and function
- already contain properties for them to function in specific layer
- Defective neuronal migration - if they are not in their correct layer, would differentiate as how they would in their supposed layer - lead to lissencephaly
Neuronal migration (‘neuroblast’ or ‘cell’ is fine)
Describe radial migration
- main way of migration
- neuroblast use leading process to wrap around radial glia cell - direct it to cortical zone
- soma of migrating neuroblast -> Somal translocation to move, actins & intermediate filaments important
neuronal migration
Describe tangential migration
- Migrating cells -> a process to find its target -> cell move my somal translocation, connexins & adhesion molecules important
- occurs in late development
- cells follow path of the cell before it
- use chemoreception
Describe the migration and layering of the cells in the cortical plate & what role does the Cajal-retzius cells play
Cells (subventricular zone) attach onto the radial glia cells and move upwards into the cortical plate.
Cells born first will move first will end up on the bottommost layer of the cortical plate.
- encounter reelin(cortical plate) secreted by the cajal-retzius cells (marginal zone) - detachment signal for migrating cells - cells laid down in the appropriate layer
- next cells migrate, migrate through layers of cells in cortical plate, encounter reelin, detach, laid down in the next layer
- cells born last - closest to marginal zone
List the development order of cells from latest (migrate last, top) layer near the periphery to earliest (migrate first, bottom) layer near the ventricular zones
Molecular layer
External granular layer (sensory)
External pyramidal layer (motor)
Internal granular layer (sensory)
Internal pyramidal layer (motor)
Multiform layer ( mixture of granular & pyramidal cells)
White matter
What happens if a women smokes during pregnancy?
What can be a cause of autism ?
- reduce migration on radial glia
- two different layer cells end up in same layer
- mis placement of certain neurons during development
What happens during neuronal differentiation?
- migrated cells -> structurally & functionally mature
- in destination, turn ON specific genes - differentiate into what they are supposed to (transcription factors or proteins)
- axons growth, dendritic growth, build synapses gene turn ON
- Cortex : Pax6, Emx2. Striatum: DARP32, Meis2. Cortex proteins: calbindin, parvalbumin
Axonal growth
- occurs at growth cones (axon ends)
- specific target to grown in which are huge distance away
-> find through chemical & electrical gradients, using many branches
-> lots of foraging for specific neurochemicals which tell correct growth direction
Dendritic growth
- connect with other axons
- occurs at GROWTH CONE
- prune excess branches overproduced in development
- remaining dendrites - continue branching & lengthening
Synaptogenesis
- happens during axonal & dendritic growth
- way billions of neurons connect & link with each other in brain
- neurotransmitter & receptors necessary - cement in synapses
