Unit 3: Neurulation Flashcards
What is neurulation ?
The formation of the neural plate and its transformation into a neural tube
What is patterning ?
The developmental process by which cells acquire different identities, depending on their relative spatial positions within the embryo
What is ‘Fate’ ?
What a cell in a certain location at a certain stage during development is most likely to become at a later stage
What is a fate map ?
A plan of an early embryo indicating the potentialities for development and differentiation of the various embryonic areas
What germ layer does the nervous system develop from ?
The ectoderm
What is the function of the node ?
It induces new axis and neurulation in prospective epidermis
What is neural induction ?
The process where certain cells in the early embryo are told to become part of the nervous system, like the brain and spinal cord.
What is the default pathway for ectoderm ?
Neural
How do you make epidermis ?
- Ectoderm
- LPM (Lateral plate mesoderm)
How is neuroectoderm formed (4) ?
1) LPM secretes BMP4 to induce epidermis
2) The notochord secretes noggin (BMP4 antagonist)
3) This allows the default neural pathway to be executed
4) Neuroectoderm is induced directly over notochord
How is the neural tube developed from the neural plate (4) ?
1) Neural plate undergoes morphogenetic changes to form neural tube
2) Primary neurulation occurs anterior to the hindlimb
3) Secondary neurulation occurs posterior to the hindlimb
What are the 5 steps of primary neurulation ? (Diagram in notes- Slide 21)
1) Initial epithelium
2) Columnarisation
3) Rolling/ Folding
4) Closure
5) Neural tube complete
What is neural closure (3) ?
- Zipping of the ectoderm
- Has 5 regions
- Failure to close at spinal chord leads to spina bifida
What are the 5 steps of secondary neurulation ?
1) Dispersed mesenchyme
2) Mesenchymal condensation
3) Medullary cord/ neural rod
4) Epithelial transition/ cavitation
5) Neural tube complete
When neural plate develops into neural tube, which of the following is required ?
1) Epithelial to mesenchymal transition
2) Presence of noggin
3) Neural crest migration
4) Convergence and extension
4) Convergence and extension
Where does primary nucleation occur ?
In the anterior part of the embryo
What happens when the neural tube is regionalised (2) ?
- The anterior of neural tube forms the brain
- The posterior of the neural tube forms the spinal chord
What genes are important for anterior posterior patterning ?
HOX genes
Describe how the neural tube acquires AP patterning ?
- Guided by retanoic acid, FGFs and Wnt
- Signalling molecules create a gradient which helps to establish the brains anterior and posterior regions
How does cell division occur in the early neural tube (4) ?
1) Height and area increases but remains 1 cell thick
2) Cells are rapidly dividing- called germinal epithelium
3) When nucleus reaches luminal surface, cytoplasmic connections with outer surface are broken and the cell divides
4) Nuclear oscillations resume
How are cell layers formed in the CNS (3) ?
1) Cells that are unable to divide detach from germinal layer and move outward
2) This generates new layer called intermediate/ mantel layer
3) Germinal layer is now called the ventricular layer
What are the 2 types of cells the intermediate layer differentiates into ?
1) Neurons
2) Glia
What is a neuroblast ?
It is an early-stage, undifferentiated cell in the developing nervous system that is a precursor to a neuron
