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 + eventually the 2 neural folds fuse to form a tube
Space in the middle = neural canal
What is the name given to the 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
Name of the wall of the neural tube
Neuroepithelium
What 3 types of cells do neuroepithelium give rise to?
Neuroblasts: all neurones with cell bodies in the CNS
Glioblasts: Astrocytes + Oligodendrocytes
Ependymal cells: line ventricles + 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 4 cell types that neural crest cells can differentiate into.
Sensory neurons of dorsal root ganglia
Autonomic post-ganglionic neurons
Schwann cells
Non-neuronal derivatives e.g. melanocytes
Describe the arrangement of the neuroepithelium.
Neuroepithelium has an inner + outer layer
Most cells are connected to both the inner + outer layer but the nuclei are at different positions
Cells actively dividing closest to inner layer
What are the 3 layers formed by the differentiation of the neuroepithelium?
Ependymal (germinal layer- lines canal) = developmental cells Grey matter (mantle layer- where neuroblasts migrate) White matter (marginal layer) = axons + processes of neurones
What guides the process of differentiation and migration?
Signalling molecules secreted by surrounding tissues
Control migration + axonal growth by attraction + repulsion
Which factors are important with regards to signalling molecules?
Concentration gradient
Timing
What can the grey matter of the neural tube be divided into? What is their orientation?
Alar plates (Dorsal) Basal plates (Ventral)
Which types of neurons do the alar plate and basal plate give rise to?
Alar plate: interneurons
Basal plate: interneurons + motor neurons
Which structures around the neural tube release signalling molecules and what effect do they have on the cells in the neural tube?
Notochord and ectoderm
Notochord signalling molecules: induce cells to differentiate into motor neurons
Ectoderm signalling molecules: inhibit cells from differentiating into motor neurons
Name the 3 primary vesicles formed from the differentiation of the wall of the anterior neural tube at ~4 weeks
Prosencephalon: future forebrain
Mesencephalon: future midbrain
Rhombencephalon: future hindbrain
Describe the changes that occur to the 3 vesicles in week 5
The 1st + 3rd vesicles divide in 2:
Prosencephalon= telencephalon + diencephalon
Rhombencephalon= pons + medulla
What important structure begins to appear at ~ 8 weeks and where does it appear from? What else starts to arise?
Cerebellum
Appears as an out pouching from the back of the pons
Ventricular system starts to arise
Name the 3 flexures in the developing brain.
Cephalic
Pontine
Cervical
Describe the arrangement of motor, sensory and autonomic cranial nuclei within the brainstem.
Motor = medial Sensory = lateral Autonomic = in between
How do neuroblasts migrate from the inner membrane to the outer membrane in the brain?
They attach themselves to radial glial cells + climb up towards the pill surface
Radial glial cells have their cell bodies anchored to the inner membrane + have a single long process to the outer membrane
How many layers of cells are there within the cerebral cortex?
6
What can a deficiency of folic acid in pregnancy lead to?
Spina bifida (No closure of base of neural tube)
What is the difference in distribution of grey and white matter in the brain and spinal cord?
Brain: Grey matter surrounds white matter
Cord: White matter surrounds grey matter
What gives rise to developmental disorders?
Genetic mutations
Environmental factors e.g. Mothers lifestyle, diet + teratogens
These interfere with the coordinated completion of the complex processes
