Development Of CNS Flashcards
Which week does the endo, meso and ecto layers become established and what do they do?
2nd week
Endo- viscera alimentary canal, respiratory and genitourinary tracts
Meso - musculoskeletal and connective tissue
Ecto- skin and nervous system
Which week does the neural plate develop and when does it become neural tube
Processes that cause neural plate to become the neural tube
3 rd week
Dorsal midline ectoderm thickens to form the neural plate
Lateral margins become elevated becoming the neural folds on either side of the depression called the -> neural tube
4th week neural tubes formed
What does the neural crest become?
Neurones with cell bodies in the PNS
Sensory ganglia
Autonomic ganglia
Schwann cells
Week of brain development and the three sections it forms
5th week 3 primary brain ventricles which can be identified Prosencephalon - forebrain Mesencephalon - midbrain Rhombencephalon - hindbrain
Defective closures of the neural tube
Anteriorly - anencephaly
Posteriorly - spins bifida
Cause massive cell division which is dependent on folic acid
Also some gene defects
- cell to cell interactions
Why does only one specific part of the ectoderm form the neural plate?
Cell to cell interactions
Mesoderm and notochord
Cell surface proteins
Extracellularly secreted molecules
Anteriorising signals are
Dickkopf and Noggin
Cause neurones to move to the front of the brain
Cell surface interaction between the forebrain and vitamin A - too much in pregnancy lead to miscarriage
Dorsal ventral patterning is by
Sonic hedge hog (Shh)
Causes ventral expression
Neocortical layering 3 steps happens in each step
What kind of organisation is this know as ?
Proliferation - in the ventricular zone cortical neuroblasts are born
Migration - they then journey to the correct positions this occurs along radial glial cells which span the primitive brain and ac as scaffolding for the movement of the cells
Differentiation - programmed before thy reach their destination when grown in culture they differentiate to the same cells. When they reach the end destination intracellular signals determined axon and dendrites once axon is fully formed the cell has no replicative potential there is differential gene activation which forms the ion channels and transmitters/ receptors
Inside out layering because the first cells to move form the innermost cells layer VI and the last cells the migrate form the outermost cells which form layer I
Inside out layering
Axon growth and connections and mediators
Axon guidance to the correct destination -
End of the axon lamellipodia with ECM proteins (laminin) these form molecular highways for neurones to travel along
Axons grow together to form white matter tracts - group into collections called fascicles via CAMs
Grow towards correct targets mediated by:
Chemoattractants - netrin make the synapse
Chemorepellents - ephrin cause axon to continue on the molecular highway
Axons express receptors which mediate this
What is synpatogeneis
2 way signalling formation between the presynaptic and postsynaptic neurones
Requires neurotrophic factors - nerve GF
What is refinement
Loss of synapses - pruning
Organised neuronal cell death - apoptosis no necrosis
Controlled by gene expression
Can also occur pathologically PD and AD potential therapeutic target
