W19-L6: Development of the CNS Flashcards
In what direction does the neural tube develop
Rostral to caudal
How many events of neural fold closure are there and which one does folate protect against?
5, each which can independently go wrong. Folate protects against stage 5 which is called spina bifida
Segmentation of neural tube
Rostral end of neural tube starts to swell and forms 3 distinct vesicles:
• Prosencephalon (forebrain)
• Mesencephalon (midbrain)
• Rhombencephalon (hindbrain)
Further segmentation of neural tube after 3 swellings
Prosencephalon splits - telencephalon and diencephalon
• Rombencelphalon – 7 segments
Neural crest cells
Cells at top of the neural tube form the neural crest, which migrate away from the neural tube to form a wide range of structures
Neural crest derivatives
Peripheral nervous system, melanocytes, Muscle cartilage and bone of skull, jaws, face
and pharynx, dentine
Neural crest migration
Neural crest cells follow specific paths through the embryo
Ventricular Zone
All neurones are born at ventricular surface (which contains stem cells) and then migrate to outer surface to add layers
What is the role of radial glia?
Neurones use radial glial cells as scaffolding to migrate across the cortex
Developmental disorders can be caused by
Cortex can be malformed as a result of mutations in genes that affect migration
Reelin mutation
Decreased folds and white matter due to poor migration of new neurones
Lissencephaly
Smooth brain due to smaller number of cells because of mutations in neuronal migration
Floor plate development
Sonic Hedgehog is released from notochord which causes the closest cells to form a floor plate which gives the direction of ventral
Role of the floor plate
Induces ventral horn motor neurones by releasing sonic hedgehog
Induction of interneurones
Ventral horn Motor neurones can tell interneurones they are more dorsal and they form interneurones (due to motor neurone factor)
What is the importance of the initial scaffold of axon tracts laid down by pioneer axons?
Guides all the other axons later on
Growth cone
A dynamic structure of cytoskeleton that is capable of crawling across a surface and pulls the axon into position
Axon navigation
Growth cone responds to local cues and grows up chemical gradients
What is the “critical period” in CNS development?
Refinement of synaptic connections that establishes mature functional nervous system
If you temporarily cover one eye shortly after birth in a kitten, then test covered eye six months later…
the eye is blind as the visual cortex has been remodelled. 2-3 weeks after birth closing the eye has less of an effect and at 6 weeks no effect
If you temporarily cover both eyes shortly after birth in a kitten, then test covered eyes six months later…
They are normal as refining connections depending on experience, if no information from one eye will choose the other, if both are covered has no information from either so cannot choose one over the other i.e no ocular dominance
