Development of the nervous system Flashcards
Briefly, What is the developmental origin of the CNS
Neural plate fold up on itself (above notochord) and forms a tube-neural tube
The neural tube walls (neuroepithelium) will develop in the CNS
Briefly, What is the developmental origin of the PNS
Neural plate fold up on itself (above notochord) and forms a tube-neural tube
At the top sits the neural crest-these cells will form the PNS
What are the 3 cell types made from neuroepithelium
Neuroblasts (all neurons with cell bodies)
Glioblasts (astrocytes, oligodendrocytes)
Ependymal cells (lining ventricules and central canal)
What are the 3 cell types made from neural crest cells
Sensory neurons of dorsal route
Post-ganglionic ANS neurons
Schwann cells
Non neuronal derivatives (eg: melanocytes (melanin producer))
Describe the organisation of differentiation of the neuroepithelium
Several layers-inside to outside
Outside (epdendymal layer) is where most developing cells are
The cells from the layer migrate to grey matter, and form white matter (axons)
Produces 3 layers in the neural tube
outside to inside (external to central): White matter, grey matter then ependymal layer (germinal layer) (most central)
What are the main principles that control neuralepithelium differetiation
Signalling molecules, their concentration gradients and timing
Control by attracting or repulsing-decide where they end up by controlling migration and axonal growth
Describe the development of the spinal cord from the neural tube
The ventral part of the neural tube - forms the basal plate => motor neurons and interneurons
At the dorsal part-alar plate => interneurons, to which dorsal root ganglia will connect to (from neural crest)
Keep this organisation in mature (butterfly shape, ventral dorsal roots, etc)
Describe the development of the brainstem from the neural tube
In the brain stem, basal plates are more medial (motor) and alar plates (sensory) are more distal
But not tube anymore- layed out more linearly and not closed (sourrounds 4th ventricule)
Describe the early development of the brain from the neural tube
From the anterior part of the neural tube
most anterior-future forbrain (Prosencephalon)
Middle-midbrain-mesenchephalon
Most posterior-hindbrain-rhombacephalon
Each are seperated with envaginations (frontal view)
But also from the side-flextures-cephalic flexture, pontine flexture and cervical flexture
Describe the development at 5 weeks of the brain from the neural tube
Fore seperates in telencephalon (cortex) and diencephalon (Hypothallamus and thallamus) (and widens)
mid stays
Hind starts widening and with pons and medulla
Describe the development at 8 weeks of the brain
start of the apparition of ventricules and hemispheres
LV/RV, connected to III, aqueduct to IV
Also cerebellum start appearing from hindbrain
At term, brain isnt fully myelinated but has the shape of a adult one
Describe the development of the cortex
Cortex-needs the folds (gyrus and sulccus)-from telecenphalon
Most inside-ventricular zone-full of radial glial cells that serve as scaffold (eventually go from ventricule to glial surfcae)
Just superior, subventricular zone - developmetal cells (even in adults)
Neurons migrate along the processes of these glial cells-from inside out
End with 6 layers, each with unique functions
What can generally lead to developmental defects
Tons of factors-genetics, diets, mother lifestyle, teratogens
What are the main forms of neural tube defects-
Either top or bottom of tube
top (B12 missing-craniocarchistis, anencephaly (no brain), encephaly (herniation), iniencephaly (extreme flexture back of head)
Bottom-Spina Biffida (not closed)-can be spina biffida occultae (cant see but inside cervical not closed). Closed spinal dystraphism)-herniation as missing vertebral arches. Menigocele-fluid filled herniation, _____-the whole spinal cord bent back
Where are the main populations of neural stem cells?
Hypocampus, ___-but adults cant really use them properly
