DEVELOPMENT OF THE NERVOUS SYSTEM Flashcards
what are the 4 stages of nervous system development?
gastrulation
neurulation
nervous system patterning
neurogenesis
what is the neural plate?
A thickening of ectodermal layer created by responses to growth factors released from the notocord
what cell types form the components of the peripheral nervous system?
neural crest cells
what day does the anterior neurophore close?
day 25
what day does the posterior neurophore close?
day 28
failure of the anterior neurophore to close leads to…
anencephaly
anencephalocele
failure of the posterior neurophore to close leads to…
spina bifida
what percentage of neural tube defects are related to folate?
70%
what factor is secreted by the floorplate cells of the neural tube?
sonic hedgehog
what factor is secreted by the roof plate cells of the neural tube?
BMP
sonic hedgehog is responsible for the formation of which type of neurone?
motor
found in highest concentrations at ventral end of neural plate
BNP is responsible for formations of which type of neurone?
sensory
found at highest concentrations at dorsal end of neural plate
what type of embryonic cells give rise to the cerebrum?
Telencephalon
what type of embryonic cells give rise to the hind brain?
Mesencephalon
how is the nervous system developed along the anterior / posterior axis?
FGF - secreted by cells in the stem zone
Retinoic acid - made by somites in response to FGF
concentration gradients of both molecules determine differentiation potentials of cells in that local area
how are the cerebral hemispheres divided during embryogenesis?
Via gradients of sonic hedgehog and FGF
what is the function of hox genes in nervous system development?
help pattern the anterior - posterior axis
combinations of hox genes are turned on and off in response to different morphogen gradients
Par3, Par6 and aPKC are all types of which family of proteins?
Apical base proteins
what is apical aposition?
The process by which neural progenitor cells undergo differentiation into neurones, by losing their apical tip proteins
what is craniorachischisis?
severe type of NTD in which both the brain and spinal cord fail to close
what is encephalocele?
sac-like protrusions of meninges through a hole in the skull (recognised in a picture as a big mass coming off a babies head)
at resting membrane potential, the membrane is very permeable to which ion?
K+
which ion is responsible for the setting of the resting membrane potential?
K+
what cell types are responsible for production of CSF?
choroid plexi of epindymal cells
what percentage of CSF is produced by the lateral ventricles?
70%
what percentage of CSF is produced by the third ventricle?
20%
what percentage of CSF is produced by the fourth ventricle?
10%
what is the recommended daily doseage of folic acid 3 months before and for the first 3 months of pregnancy?
400ug/day
what are the consequences of too much folate in the diet?
folate transporter in choroid plexus blocked
can lead to early onset dementia
what is the average volume of CSF in an adult?
140-270ml
how much CSF is produced per day in an adult?
600-700ml
what is tethered spinal cord syndrome?
complication of open SB in which cauda equina becomes entangled within spinal cord coverings, causes paralysis as growth stretches spinal cord
in the case of a meningomyelocele, what substance is damaging the nerves exposed in the cele?
Amniotic fluid - foetal urine
what percentage of pregnancies are insensitive to folate?
33% (one third)
what percentage of spina bifida cases go on to develop hydrocephalus?
50%
which two genes are functionally analogous to the hox genes in terms of patterning of cerebral development?
Emx and Otx
at approximately what day does the cerebral cortex start to develop?
week 8
why is CSF drainage critical to normal cerebral functioning?
we need to drain around 400ml per day to maintain constant level of CSF
why is drainage of CSF described as an active process?
ependymal cells are a type of simple columnar glial cell that line the ventricles.
They waft CSF out of the ventricles into sub arachnoid space.
Lack of ependymal cells can produce congenital hydrocephalus
what is the difference between dietary folate and folic acid?
dietary folate > 5-methyl-THF
folic acid > Dihydrofolate
methyl group in dietary folate used for DNA methylation. folic acid doesn’t have that!
along with folate, which vitamin is needed for efficient folate function?
Vitamin D
