Development of the Central Nervous System: Gondre-Lewis Flashcards
Repeat of Ziermann
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somites give rise to
segmentation of the body plan
The ectoderm gives rise to what?
nervous system, integument, pigment cells
The mesoderm gives rise to what?
bones, muscles, connective tissue, blood vessels
The endoderm gives rise to what?
gastrointestinal tract, lungs, liver
What are the mesodermal derivatives?
Paraxial Mesoderm: closest to midline; thick; forms somitomeres which give rise to mesenchyme of head and organize into somites at occipital and caudal levels to eventually form vertebral column, limb, body wall musculature
Intermediate: Urogenital system
Lateral Plate Mesoderm: thin, lateral; line peritoneal, pleural, and pericardial; thin membrane around each organ, vessels, etc.
send signals to one another to induce each other’s formation
notochord formation
forms the body its longitudinal axis; gives body the left and right demarcation
-signals that set the midline of the CNS as it develops (brain)
- notochord has cranio-caudal axis of formation
- solid rod, important in establishing body’s longitudinal axis
- mesodermal origin
- induces columnar epithelial celsl above to become the neural plate
parts of mesoderm that migrated first are part of the cranial
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What is the first event in the formation of the nervous system?
formation of the neural plate
- inducing substances from notochord diffuse to epiblast and activate gene transcription
- cells differentiate into a thick plate of columnar epithelial cells: thickening of epiblast layers cranial to the primitive pit; differentiates craniocaudally
concomitantly with the somites
- see hindbrain at Day 20
- formation of neural plate is the first event in the formation of the nervous system
How does induction take place? How are axes established? What are organizers?
- as they migrate through the primitive node they change their identity
- any mesodermal that migrates through primitive node and cranially will be paraxial mesoderm
What are examples of organizers?
Bone Morphogenetic Protein-4 (BMP-4) – ventralizing signal for Intermediate Mesoderm and Lateral mesoderm (as it goes through the node this is no longer expressed (antagonized)
-Chordin, Noggin, Follistatin antagonize actions of BMP-4 (and;FGF).
They don’t get antagonized with chordin, noggin???
????on the Mesodermal Derivatives slide
Molecular regulation of neural induction !!
How are axes established?
BMP-4 in ectoderm
cranial-caudal axis
ventral-dorsal axis
if BMP-4 is activated ectoderm becomes neuralized
where the midbrain and forebrain form will be induced by chordin, noggin, and follistatin????
caudal neural plate structures (hindbrain & spinal cord) depends on different secreted proteins from notochord, Wnt-3a and FGF, as antagonizers of BMP-4
Why is retinoic acid also an important organizer?
induces those homestatiic HOX gene expression
closest to the neural tube
farthest to neural tube
ventral????
skin (dorsal)
They change the shape of the overlying tissue
the ends have a different influence than the ones on the midline
the change of the shape of the columnar???to form the ectodermal ridges
as this rises this confirmational change of the overlying ectoderm that is no longer influenced by the?????
neural tube formation ends by 26 days
closing of neural tube at day 24
15-26 you get induction of the neural plate and closure of the neural tube
Neural crest cells
- we have somites of mesodermal origin
- the spaces in the neural tube will become ventricles of the brain (with CSF)
- the arrows represent the migration of the neural crest cells
- the fate of the neural crest cells is controlled by the local environment of the body
for example: cells that take superficial pathway, just beneath the ectoderm will form pigment cells of the skin
-completed by day 26
What are neuronal derivatives?
ganglia of the PNS
- dorsal root ganglia
- autonomic sympathetic chain ganglia
- parasympathetic ganglia
- cranial nerve ganglia
neural-like cells of the adrenal medulla
-important support cells
EVERYTHING THAT IS NOT CNS!!! (EXAM QUESTION!!)
Secondary neurulation
develops CNS up to somite day 37
-this process ???
neural tube defects
it is not related to a specific race you find them in hispanics, white, AA
-at some point UK was shown to be greater than JApan (associated with diet)
there are different places where the above can happen
anterior notocord does not enclose properly
posterior notochorddoes no enclose properly
spina bifida where it occurs at the level of the spinal cord
occulta
meningocele
meningeomyocele is the most severe: neural tissue is sitting outside of the bony cavity and is exposed to the external environment
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Holoprosencephaly
cranio-facial anomaly
The eye and retina are nerual srtuctures
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from the mesenchyma ????? and spinal cord
What becomes the cerebellum?
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prosencephalon, mesencephalon, and myelocephalon
have different organizers that demarcates boundaries
Hox genes are organizers of the hindbrain.
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Cytodifferentiation
cells that give rise to the
that single neural epitheliual cell the first cell it generates give rise to neuroblast–>neurons
?????
alar plate
sensory association area
basal plate
motor neurons
4 slides showing the same thing what thing??
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What is the major difference between the brainstem and medulla?
???
Forebrain is like the SC and the brainstem except
it is more complicated
- instead there are more rounds of neuroblasts differentiation ( the cerebral cortex ????)
- layering occurs in an inside-out pattern of lamination
- more complex
-grows out of ventricular zone proliferations (radial migrations)
tangential migration
- medial ganglionic eminence that travel far form their birth to reside in Layer IV of the cerebral cortex; give rise to interneurons
- rostral migratory stream
What is the difference between radial and tangential migration?
test questions????
Lissencephaly
smooth brain when there errors in migration (failure of induction of migration)
How does the axon know where to go?
- it needs to follow molecular cues (some are repulsive or attractive or both
- growth cones
commissural axons
anything that crosses the midline
Robo is a repulsive to slit and silences DCC
the farther away from midline the axon goes
Agenesis of the corpus callosum (ACC)
there is a lack of axon guidance occurring to get it to where it needs to go cross the midline
