CNS Development Flashcards
what week does development of the brain begin?
3rd week post-conception and continues into early adulthood
what do genes determine?
correct sequence and evolution with neuronal proliferation, migration and reorganisation
development of dendritic and axonal interconnections
development of synapses, receptors and neurotransmitters
two types of environments that influence brain development
intrauterine
extrauterine
how does the intrauterine environment affect brain development?
maternal heath and disease (maternal PKU risks crossing placenta and affecting the brain)
insults that are continuous or episodic during pregnancy e.g. alcohol or CMV
placental nutrition (delivery failure risks intrauterine growth retardation)
how does the extrauterine environment affect brain development
- physical factors e.g. nutrition and environmental toxin
- emotion and social factors e.g. neglect and lack of stimulation
- exposure to drugs, alcohol and other related substances
four stages to brain development
embryonic
foetal development
post-natal development
adolescent brain
time frame of embryonic brain development
conception to week 9
how does gastrulation and the three layered embryo formed?
the two layered embryo consists of epiblasts and hypoblasts between which the primitive streak/node has cells migrate through (route of migration is determined by nodal signalling)
three layers of the embryo
ectoderm= skin, nails, hair and neural tissue mesoderm= muscle, bone, cartilage and vascular system endoderm= gut and respiratory system
what days does the neural tube form
day 20-27
describe the formation of the neural tube
neural progenitor cells form neural plate which develops a groove and folds into a tube. the progenitor cells line the tube (ventricular zone). hollow centre becomes the ventricular system and central channel of the spinal cord
what does the rostral tube become?
brain
what does the caudal tube become?
spinal cord
signalling molecules
Pax6
Emx2
what does high concentration of Pax6 and low concentration of Emx2 cause
progenitors become motor neurone in the anterior and rostral area
what does low Pax6 and high Emx2 induce?
visual cortical neurones (posterior/caudal)
how does the appearance of the brain change in foetal development?
brain is initially lissencephalic and gradually develops a folded appearance (sulcal and gyro pattern- accommodates more neurones)
formation of three sulci
primary= week 8-26 seconday= 30-35 teritary= 36 to early infancy
describe brain development in foetal stage of CNS development
- neuronal progenitor cells in the VZ divide to form two identical progenitor cells (days 25-42)
- asymmetrical division follows producing one progenitor cell and one neurone (post-mitotic, loss cannot be re-established)
- migrate to developmental neocortex
two main processes in post-natal development
- proliferation and migration= limited in VZ but does happen elsewhere
- myelination
describe the process of myelination in post-natal development
oligodendrocytes progenitor cells wraps around axons (myelin sheaths)
what does myelination cause?
increased conduction rate
axon integrity
diameter
survival
direction of myelination formation
bottom to top
back to front
what input is needed post-natally
environmentally diverse and experiences
what happens during adolescent brain development?
reorganisation of the brain with many synapses eliminated, increase in white volume and change in neurotransmitter system
what does monocular visual deprivation cause in later life
altered organisation of primary visual cortex as both eyes develop dominance columns, if one eyes becomes blocked the band shrinks and the active eye invades this territory
what do insults during neural tube formation lead to?
anencephaly
spina bifida
insults during development of brain vesicles
holoprosencephaly
disorders of myelination
hypermyelination
dysmyelination
demyelination (formed then lost)
what does the PLP1 gene code for?
myelin protein present in CNS
what is myelin protein responsible for?
compaction, stabilisation and maintenance of myelin sheaths
oligodendrocyte development
axonal survival
where is the PLP1 gene located?
X chromosome (boys)
most severe form of mutation in PLP1 gene
Pelizaeus-Merzbacher
presentation of PLP1 gene mutation
infancy/early childhood nystagmus hypotonia cognitive impairment progresses to severe spasticity and ataxia life span shortened
impact of malnutrition
brain growth and volume
myelination
energy and deprivation (experience and stimulation)
disease and debilitation
