0217 Flashcards
Six steps for mature central nervous system
Proliferation, migration, differentiation, axon pathfinding, synapse formation, regressive events
What is proliferation
Mitotic activity, form billions of cells from dozens
What is migration
Some cells leave to form distant nuclei and layers, they aggravate in these layers
What is differentiation
Chemical and morphological differences that determine group and function
Regressive events
Neurons overgrow then they prune back extra axons den dries etc.
What is a blastula
Single Ball of cells
What is the earliest event in the nervous system
Neural induction (proliferation)
When does neural induction happen
Gastrulation
What is gastrulation
A stage where enormous cell movements (invagination, inggression, and involution) lead to the formation of three germ layers
What are the three germ layers
Ectoderm, mesoderm, endoderm
When are the primary body axes established
During gastrulation
What interaction is critical for the specification of neural cells
The interaction between dorsal ectodermal and mesodermal cells along the midline
What does the dorsal ectoderm become
Neural plate
What does the Neuro plate become
Neural tube
What happens to the rest of the ectoderm (minus the dorsal ectoderm)
It developed into skin
Which germ layer is the basis for the vertebrate nervous system
The dorsal ectoderm
Which germ layer is crucial for the development of the invertebrate nervous system
Ventral ectoderm
Where do melanocytes in chromaffin from the adrenal glands come from
Dorsal ectoderm
What type of signaling is used in the invertebrate ventral ectoderm
Delta notch signaling
What is delta notch signaling
Communication between adjacent cells rather than regions
How do vertebrate ectoderm communicate
Chemical signaling from the mesoderm to ectoderm
What neurons come from the neural tube
Central nervous system neurons
What neurons come from the neural crest
Peripheral nervous system neurons
What forms neural groove
The sides of the narrow plate fold up from the cell shaped changes of neural plate cells in ectodermal proliferation; invagination
What makes certain cells go towards the notochord
Cell adhesion molecules
What is the collection of cells between the neural tube in the epidermis called
Neural crest
And the neural crest, what does the low concentration of anti-BMP expressions do
They increase mutual binding of BMP four on the TGF beta receptor
What happens when tissue is transplanted from the dorsal blastopore lip before the pre-gastrulation stage
It will grow a second nervous system composed of host cells
What is the finding that lead to the neural induction hypothesis in the effort of identifying neural inducer molecules
Ectoderm has switched from epidermidis to neural ectoderm when a second nervous system is created
What effect does the blastopore lip have on the ectoderm
it induces it to become neural
What will happen to uncommitted ectoderm cells
They will become Nuro ectoderm cells and they will produce neurons and glia
What are the two experiments that help with understanding of neural induction
Implant liver with aldehyde treatment and transplantation of tissue from dorsal blastophore lip of a donor newt
What happens when ectodermal cells secrete BMP-4
This causes the ectodermal cells to become epidermal cells instead of neural cells
Why did the isolated cell culture not become epidermal cells
The BMP – four was too diluted
What is the receptor for a BMP 4
TGF Dash Beta
What are the four competitive antagonist of BMP – four
Noggin, Chordin, ceberus, and fallistatin
What happens when BMP antagonists bind to its receptor
The ectodermal cells stay default into neurons
What does noggin binding do
It makes neurons
What does chordin binding do
Induces neural tissue and other tissue
What germ layers produce the BMP-4 antagonist proteins
The dorsal blastopore lip & the midline mesoderm
What turns off pro neural genes and turns on epidermal genes
Smed timer
What is the Pathway for epidermal to form
BMP – four vines to TGF Beta which activates smad 2 to bind to smad 4 for and the dimer goes to nucleus
What is another name for the notochord
Dorsal mesoderm
What happens to the inhibitors of BMPs that the dorsal mesoderm releases
They diffuse into the dorsal ectoderm and block the effect of BMPs to allow neural tissue to form
During what stage of mitosis does the local environment instruct cells to become one type over another
The last stage
What are the two main migratory paths for neural crest cells
The ventral migratory pathway & the dorsal migratory pathway
What do neural crest cells on the dorsal pathway become
Melanocytes
What do neural crest cells on the ventral Pathway become
Dorsal root ganglion neurons, I don’t gnomic ganglion cells, adrenal chromaffin cells, or enteric ganglion cells
How do you produce a symmetric division
Vertical cleavage that splits perpendicularly to ventricular surface produces symmetric division
What happens as a result of symmetric division
Both daughter cells attached to the ventricular surface and both re-enter mitosis
What are the two ways to produce asymmetric division
One. A horizontal cleavage that Cleaves parallel to ventricular surface
2.. If a cleavage plan is off centered vertically
What happens as a result of asymmetric division
The daughter cell with the attachment to the ventricular surface reenters mitosis, and the one without the attachment exits mitosis, migrates away, and undergoes differentiation
What is the division type that cells undergo in proliferation
Symmetric division
What is interkinetic nuclear migration
Neuroepithelial cells attached to both the inner surface of the neurotube and it’s out of surface. Individual nucle and migrate upward and back down during S and the G phases of mitosis
What type of division happens at places that form layer structures i.e. retinal cerebral cortex cerebellar cortex
Asymmetric division of the neural epithelium cells
What is the benefit of asymmetric division in terms of the population size
One cell staying in the cycle allows for preparation
What are the first and last cells to leave in the retina
The first cell to leave are the ganglion cells and the last cell to leave are the bipolar and Mueller sales
What is the timing of different cell types being born
Cells of different types are born at different times
What are the two proliferation zones
The cell zone & the ventricular zone, mantle
What are one of the first specialize cells to be generated in the neural tube
The radial glia
What cells give rise to the progenitors that divide to produce post mitotic neurons
Radial glial cells
What distance do the radial glia cells span
Ventricular surface to the outer surface
What are the majority of stem and progenitor cells in the ventricular zone
Radial glia
What do the radial glia proliferate and form
Radial glia, neurons, and glial cells
How do cerebellar cells and cortical cells migrate
Along to radial glia
What regions does the spinal cord divide into
Alar/dorsal plate and basal/ventral plate
What does the dorsal horn of the spinal cord develop into functionally
Somatosensory
What does the ventral horn of the spinal cord develop into functionally
Motor functions
From medial to lateral what are the three zones of the spinal cord
Ventricular zone where all proliferation takes place; intermediate or mantle zone where post mitotic cells migrate; marginal zone where the processes of neuroblasts are found
What is the sulcus limitans
It is the hole and the middle of the spinal cord so that the zones aren’t touching each other
Which zone is the gray matter of the spinal cord And develops into the dorsal and ventral horns
The intermediate zone
Which zone becomes a white matter of the spinal cord
The marginal zone
What happens in the marginal zone
Ascending axons from the spinal cord to the brain and descending axons from the brain to the spinal cord occupy that zone and become myelinated. No cell bodies
What is outside outmigration
In the mantle zone, the earlier generated neurons migrate toward the outer surface and end more laterally in the gray matter whereas the later generating neurons end more medially in the gray matter
What do the first set of neurons that migrate from the proliferating ventricular zone form
The pre-plate
How is the cortical plate formed
Later generated cells migrate to the preplate to form the cortical plane
What are the two layers of the preplate after the cortical plate is formed
The marginal zone and the sub plate zone 
What does the ventricular zone divide into as it gets thicker
The subventricular zone & the intermediate zone
How are the critical layers formed from 6 to 2
Cortical plate neurons form the layers after all the proliferation happens
What do the cortical neuron axons occupying the intermediate zone do
Form the white matter
What neurons die off in a late development stage of the cortical plate
The mariginal zone and subplate
What is inside out migration in cerebral cortex
The earliest set of neurons that migrate toward the pia surface (basal surface) to the pre plate form the cortical plate. There the neurons mature and form the deepest layer 6 of cortex. Neurons of subsequent migration into the cortical plate must go through layer six.
What cells secrete Reelin
Cajal-retzius cells
What is the benefit of the secretion of the protein reel in
It attracts post mitotic neurons toward the marginal zone and allows them to move past the earlier migrating neurons of the cortical plate
How is a cerebral cortex arrange when there is a mutation in reelin
At least to an upside down cerebral portex and which the earliest born neon occupied layer two and the last born occupied layer six.
What happens to the processes of radial glia in an upside down cerebral cortex
They grow chaotically toward the pial surface and rather than forming separate populations CR cells and subplate neurons around occupy the region of the marginal zone
What percentage of neurons are inhibitory in the cerebral cortex
20%
How do excitatory neurons of the cerebral cortex reach the appropriate layer
Radial migration
How do inhibitory neurons reach cortex and get to proper layer
They reach the cortex by tangential migration and then they go to the correct layer using the radial glia
Where are inhibitory neurons generated
Ganglionic eminence
How do inhibitory neurons stay on track when they are on their tangential path
They take cues from secreted or cell surface proteins that repel them from entering other regions and attract them to their appropriate regions
Where do gabba neurons leave from
Medial and lateral ganglianic in eminences
What is the target for gabba neurons
They leave the lateral and medial ganglion eminences to reach the striatum, areas of Paleo cortex, neo cortex and hippocampus
What are the two roles of the radial glial cells during the mid period of neurogenesis
The first role is to divide and form dedicated neuronal progenitors that will form specific types of post mitotic neurons and the second role is to stay attached to both surfaces of the neural tube and provide a scaffolding along which post mitotic neurons can migrate
In adult animals what do radial glia turn into and the subventricular zone that enables them to re-enter mitosis to generate more neuronal progenitors
Astrocyte
Where do neuronal progenitors give rise to neurons in adult animals
The sub ventricular zone near the lateral ventricles & the sub granular zone of the dentate gyrus (pattern completion)
What is special about the dentate gyrus that allows it to do pattern separation
the sub granular zone of dentate gyrus neuronal progenitors give rise to new neurons even in adults
Where do a large fraction of sub ventricular zone progenitors ago
They enter the rostral migratory system
Where do progenitors that enter the rostral migratory system go
They reach the olfactory bulbs to become part of the olfactory bulb circuitry
When the layer 4 cerebral cortex cells start to migrate, what populations of neurons are already present in the cerebral cortex?
Cajal Retzius cells, subplate neurons, and cortical plate layers five and six neurons
What population of neurons does not require the radial glia?
Cajal-Retzius cells migrate by simply nuclear movement
What two proteins determine the proper laminar or complex of the cortex?
Reelin & semaphorin 3A
What role does reelin play
Supports migration of later born cells past previously born cells
What role does semaphorin 3A play?
Repels axons from the cortical surface, forcing them to invade the white matter
What protein instructs dendrites of excitatory neurons to go toward the surface of the cortex
Semaphorin 3a
What happens during the development of inhibitory neurons that accounts for the radical difference in expression between excitatory and inhibitory neurons of cerebral cortex?
Inhibitory cells are generated at a separate location (ganglionic eminence) and take a different migratory path (tangential migration) to cortex
What chemical factors secreted by different parts of mesoderm compete to determine whether overlying ectoderm will be skin or neural?
BMP – number four competes with the anti-BMPs
What specific region of mesoderm makes and secretes BMP for
Ectoderm makes BMP – four whereas Noto chard makes anti-Bmps
What is a population of non neurocells that are derived from Nu crest and the chemical factors that drove these neural crest derivatives to adopt a nonneral fate?
Adrenal chromaffin cells become non-neural when exposed to glucocorticoids made by adrenal cortex
Which of the five regions of embryonic central nervous system would you transplant from a donor to a hose to induce ectoderm to become lens
Diencephalon
What happens during asymmetric division that triggers the switch from a neurono precursor to a glal precursive
Sequestration of numb at one pole of the progenitor cell drives all of it into one daughter which will become the neuron, and none of it into the second daughter, which becomes a glial precursor
What biochemical event triggers the switch from an astrocyte precursor to an oligodendrocyte precursor
There is a suppression of Delta – notch signaling and the precursive cell fuels the switch from APC to OPC
When a donor is implanted in a host, does the donor grow its own selves or does the donor induce the host to grow its own
The donor induces
What chemical signal molecules do the cells of the notochord
The Noto chores sells secrete the anti-BMP‘s
Are anti-BMT permissive or instructive cues
They are permissive cues because they do not actively signal a cell to adopt a particular fate but they do serve to block a cell from entering and epidmal fate
What regions of the nervous system arise from the margins of the Neuro plate
The neural crest and roof plate
What happens to the shape imposition of pyramidal cells when the reelin gene is knocked out
They would take unusual paths and no longer reach toward the surface of the cortex; it will be a flit cortex with layer six at top
What towels the axons of the old factory sensory neurons to hold off their invasion of the old factory bulb until the bulb neurons are there and ready
Sema-3a is the signaling molecule that prevents OSN axons from entering the brain until the bulbs are ready for them
What type of precursor cell remains capable of proliferation in adult animals?
Radial glial cells form astrocytes in the sub ventricular zone that remain proliferative in adult mammals
By the 25th day post conception, the brain and spinal cord for my simple tube with a couple of bends called what?
Flexure
Where is the cervical flexure
It is at the junction of the spinal cord and rhombencephalon
Where is the cephalic flexure
It is at the junction of the rhombenCephalon and mesencephalon
What are the three parts of the brain that you can see by the 25th day
The caudal most rhombencephalon, the middle mesencephalon, and a rostro procencephalon
What does the rhombencephalon split into
The Mylan Cephalon and the metencephalon
What is the common terminology for the myelencephalon
The medulla
What is the common name for the metencephalon
The pons and cerebellum
What does the prosence Cephalon do
Diencephalon & telencephalon
What is the common name for the mesencephalon
Midbrain
How many days post conception does it take for the five segments of the brain to develop
35 days
What results did we find when Spearman transplanting tissue in a different size are embryos and gastrula stage
Only transplants from the blastopore lip induced surface ectoderm to become Nuro ectoderm. V
 In a second experiment what happened when they took the ectoderm from the dorsal cab before gastrulation and dissociation the sales
It automatically became neural tissue
