Development of the Nervous System Flashcards
Define neurolation
The process during which the neural plate forms the neural tube.
How does the neural plate form?
The ectoderm differentiates into an outer surface ectoderm which gives rise to skin and inner neuroectoderm, which thickens to become the neural plate.
How does the neural tube form?
Cells at the lateral edges of the neural plate proliferate and form elevated neural folds that fuse.
What is the neural crest?
During neural tube closure, cells on the crest of the neural folds detach and form a new cell population.
Describe neural tube defects
Anencephaly: Defective closure of the anterior neuropore.
Spina bifida: Defective closure of the posterior neuropore and incomplete fusion of the posterior vertebral arch.
Distinguish spina bifida occulta from spina bifida cystica.
Occulta: Marked by tuft of hair
Cystica: herniation of meninge and/or spinal cord through vertebral arch
Distinguish spina bifida cystica meningocele from Meningomyelocele
Meningocele- Protrusion of meninges and CSF but not spinal cord.
Meningomyelocele: Protrusion of spinal cord and meninges into a cyst.
How does the primary brain vesicles form?
The neural tube closes at the anterior neuropore and forms three bulges
Describe the 3 zones of the neural tube.
Ventricular zone: Innermost layer where neurons of the CNS, glial and ependymal cells fom.
Intermediate zone: Middle layer containing alar and basal plates
Marginal zone: Outermost layer that produces white matter of spinal cord
What happens once the 3 zones are made?
A crease called the sulcus limitans divides the neural tube into an alar plate dorsally and a basal plate ventrally.
What does the alar plate contain? Basal plate?
Alar plate: Contains neuroblasts that create sensory neurons and interneurons; Dorsal horns
Basal plate: Neuroblast that forms motor and interneurons; Ventral and lateral horns.
What are the roof and floor plates?
Where neuroblasts are absent during neural tube development. The notochord uses sonic hedgehog to tell cells to make the floor plate. The overlying ectoderm uses Bone morphogenetic proteins to make the roof plate.
Where is most neuronal proliferation done in the forebrain?
In the subventricular zone, adjacent to the lateral ventricles
Define synaptic pruning
The process of reducing the overall number of neuron processes and synapses during development, leaving only the most efficient.
Discuss Myelination
Starts about six months into development, peaks during the first year after birth and continues into adulthood.
