CNS Development Flashcards
Which structures human embryonic disk are relevant for embryonic development?
primitive streak and Hensen’s knot
Which structure connects the human embryonic disk to the uterus?
body stalk
what are the 2 bubbles of the human embryonic disk? What do these bubbles contain?
allantois (containing yolk sac) and amnion (containing ectoderm)
label the human embryonic disc diagrams
see slides 1 and 2
Which animal is neurulation in humans similar to?
chicks
What is the first step of neurulation?
embryonic disc folds into the neural groove
how many days does neurulation take in chicks? humans? (i.e. when does the neural tube fully close?)
- chicks: 1 day
- humans: 24 days
why does the embryonic disc narrow firstly in the central region during neurulation?
- LATERAL EPITHELIAL CELLS in that area proliferate very fast and push the neural crest toward the center of the disc
- MESODERMAL CELLS proliferate fast and fill the space between the ectoderm and endoderm, causing neural crest cells from both sides to meet in the central region
TRUE or FALSE: the neural crest differentiates into the CNS and the neural tube differentiates into the PNS
FALSE: neural crest becomes PNS and neural tube becomes CNS
What is the notochord’s function initially? finally?
- initial: mechanically stabilize tissue (between neural groove and endoderm)
- final: release factors to signal for neural tube cell differentiation
what do the mesodermal somites show in the final stage of neurulation?
transversal segmentation
what results when the neural tube does not close at the anterior end?
- anencephaly
- forebrain and skull do not develop
- stillborn baby (lethal)
what results when the neural tube does not close at the posterior end?
- spina bifida
- major functional deficits such as dysfunctional motor control or epilepsy
- baby can survive if only lowermost part of spinal cord is affected (non-lethal)
is spina bifida lethal?
no
is anencephaly lethal?
yes
what is a non-inherited way of getting spina bifida?
dietary deficits in cholesterol or folate (i.e. folic acid or vitamin B9)
Which endogenous ectodermal protein is pivotal for neural tube closure?
N-cadherin
which part of the neural tube produces N-cadherin? E-cadherin? What is the function? What does each signal for?
- N-cadherin produced by neural plate; signal for neural plate proliferation
- E-cadherin produced by presumptive epidermis (lateral); signal for epidermal proliferation
What occurs when presumptive epidermal cells are manipulated to genearte both N-cadhrein and E-cadherin?
one side of the neural tube does not enfold –> therefore tube cannot close
(i.e. signalling molecules are VERY IMPORTANT for CNS development)
What does the optic cup form later on?
retina
where does majority of the proliferation occur?
telencephalon, diencephalon, optic vesicles
(i.e. forebrain)
draw slides 6-8
draw
which part of the telencephalon has a thicker cell layer?
ventrolateral (adjacent to diencephalon)
draw development of antenatal forebrain
see slide 8
what does the diencephalon differentiate into?
hypothalamus and thalamus
Describe the thalamus relay sensory path for the eyes.
eye –> thalamus –> cerebral cortex
Describe the thalamus relay sensory path for the ears.
ear –> interneuron? –> thalamus –> cerebral cortex
Describe the thalamus relay sensory path for the skin.
skin alpha neuron –> interneuron? –> thalamus –> cerebral cortex
draw the development of the spinal cord tissue differentiation
see slide 9
What does the central aspect of the spinal cord tissue comprise of?
neuronal cell bodies (somata) and astrocytic glial cells surrounding the spinal/central canal (grey matter)
TRUE or FALSE: dorsal horn contains sensory tracts and the ventral horn contains motor tracts
TRUE
what is the name for a progenitor cell that develops into a neuron?
neuroblast
what type of neurons does the intermediate zone of the spinal cord contain?
interneurons (for locomotion and reflexes)
Describe the differentiation process of a neuroblast.
- develop very large and complex dendritic tree via which info is received
- axon branches out (may look like dendritic tree)
What are the paracrine signaling factors of the spinal cord?
- Shh (sonic hedgehog)
- TGF (tumor growth factor)
- BMP (bone morphogenic protein)
Which part of the neural tube secretes Shh? Where do they diffuse into?
notochord –> floor plate
Which part of the neural tube secretes BMP? Where does it diffuse into
ectoderm –> roof plate
Draw a diagram to describe how signalling factors affect neural tube differentiation.
see slide 10
Describe how signaling factors affect neural tube differentiation.
- Shh secreted from notochord; BMP secreted from ectoderm
- Shh diffuse into floor plate; BMP diffuse into roof plate
- Shh causes snowball effect leading to release of other factors from the roof plate: TGF family (BMP 4, 5, 7, Dorsalin, Activin –> BMP7, Dorsalin, Activin –> Dorsalin, Activin)
- Shh gradient and TGF gradient formed
Draw protein expression and transcription factors
slide 10
top: TGF
middle: Shh
bottom: motor neurons
What do radial glial cells eventually develop into?
astrocytes
what are the zones of the telencephalon wall at the beginning of neuronal migration.
ventricular zone, subventricular zone, intermediate zone, cortical plate, marginal zone
In which layer of the telencephalon wall do neurons first differentiate?
subventricular zone
What ion channels are found on the leading process of a migrating neuron?
Ca2+ channels
What ion channels are found on the trailing process of a migrating neuron?
K+ channels
What do migrating neurons travel along?
radial glial cell process
What is the development order of the final layers of the cerebral cortex?
VI –> V –> IV –> III –> II –> I
Why is the development of the cerebral cortex layers called “inside-out”?
younger neurons do not attach to older layers from the inside, but migrate through these old layer to the outside of the cortex
Which layer of the cerebral cortex contains NO neurons? What does it contain instead? What is its function?
- layer I
- epithelial and glial cells
- isolates cells from fluid
Which layer of the cerbral cortex contains axons?
white matter
Which ion plays a major role in cell division?
Ca2+
Which ion plays a major role in cell migration?
Ca2+
Describe the events and role of Ca2+ in cell proliferation.
- progenitor cells divide to form a neuroblast layer
- neuroblasts become active and secrete GABA (inhibitory)
- during development, GABA is excitatory and depolarizes progenitor cells
- depolarization causes influx of cytosolic Ca2+
- Ca2+ rise STOPS proliferation of progenitor cells
Describe the events and role of Ca2+ in neuroblast migration.
- SST stimulates migration via fast Ca2+ rises
- cells move to granule layer
- SST stops migration via SLOWING Ca2+ rises, in order to make the granule neurons stay in the granule cell layer
