Development of the Nervous System Flashcards
What is the name given to the proliferation of the ectoderm in the dorsal midline?
Neural plate
What happens to the neural plate as it thickens?
It folds up the sides and eventually the two neural folds fuse to form a tube
The space in the middle is the neural canal
What is the name given to the bunch of cells at the tip of the neural fold that are excluded in the fusion?
Neural crest
Which cells do the neural tube and neural crest cells give rise to?
Neural tube – all cells of the CNS
Neural crest – all cells of the PNS
What is the name given to the wall of the neural tube?
Neuroepithelium
What three types of cells do neuroepithelium give rise to?
Neuroblasts – all cells with cell bodies in the CNS
Glioblasts – these become neuroglia (astrocytes + oligodendrocytes)
Ependymal cells – line the ventricles and the central canal
Are motor neurons produced from neuroepithelium?
Yes – although most of their axons are outside the CNS, their cell bodies are within the spinal cord
State four cell types that neural crest cells can differentiate into.
Sensory neurons of dorsal root ganglia and cranial ganglia
Autonomic post-ganglionic neurons
Schwann cells
Non-neuronal cells e.g. melanocytes
Describe the arrangement of the neuroepithelium.
Neuroepithelium has an inner layer and an outer layer
Most cells are connected to both the inner and outer layer but the nuclei are at different positions
Describe the differentiation of the neuroepithelium.
Firstly, you get cells withdrawing away from the outer membrane towards the inner membrane where it undergoes mitosis
One of the daughter cells will remain attached to the inner membrane and the other daughter cell will move away from the inner membraneand become a neuroblast
The neuroblast will develop processes and one will become the axon
These axons are directed away from the inner membrane
Three layers are formed
What are the three layers formed by the differentiation of the neuroepithelium?
Ependymal, grey matter and white matter
AKA germinal layer, mantle layer, marginal layer
Glioblasts show a similar pattern of differentiation to neuroblasts. State one difference.
Glioblasts can migrate into the white matter
NOTE: glioblasts do not develop axons (but they do develop processes)
What guides the process of differentiation and migration?
Signalling molecules
Which factors are important with regards to signalling molecules?
Concentration and timing
What can the grey matter of the neural tube be divided into?
Alar plates and basal plates