Development of the Nervous System Flashcards
When do the first signs of nervous system development occur?
- 3rd week of gestatio
From where are the first growth factors secreted which influence growth in the 3rd week of gestation?
- The notochord
What is the neural plate and where is it?
- The first developmental neural structure consisting of ectoderm surrounded on either side by neural folds which is a precursor to the neural tube
- Occurs in the dorsal aspect of the embryo
What is the neural groove?
- A shallow median groove between the neural folds of an embryo
Once you have the neural plate, describe the deelopment of the nervous system up until the 4th week of gestation - just in terms of neuralation
- The neural plate broadens and folds to form the neural groove
- The neural plate folds at the neural groove to from the neural tube
- The fusion begins approximately halfway along the neural groove at the level of the 4th somite and continues caudally and rostrally with the closure of the posterior / caudal and anterior / rostral neuropore during the 4th week of gestation in neuralation
- Note neuralation refers to closure of the neural tube
What do the cells of the Neural Crest give rise to?
- The DRG (dorsal root ganglia)
- The peripheral components of the ANS
What is the name of the distal tip of growing neurites or neurones which responds to growth factors?
- The growth cone
When the neural tube closes, what runs along the middle of it - essentially the lumen of it, and what does this develop into?
- The neural canal which develops into the central canal in the adult brain
Describe the cells distribution along the developing neural tube and how they go on to form the ependymal layer, and the gray matter and the white matter
Excluding the neural crest / epidermis
- Neuroblasts line the ependymal layer
- The neuroblasts along the ependymal layer divide and migrate out to the mantle layer where they differentiate into neurones to form the grey matter of the spinal cord
- The developing processes from the neuroblasts / neurones grow out into the marginal layer, where they develop the white matter of the spinal cord
Describe the dorso-ventral patterning of the developing neural tube and what drives this
- The developing neuroblasts separate into 2 discrete populations - the dorsal group forming the alar plate and the ventral group forming the basal plate
- The alar and basal plates create the dorsal (sensory) and ventral (motor) horns of the spinal cord and at their interface in the thoracic and upper lumbar cord you can find the small lateral horm of visceral efferent neurones (part of the ANS)
- This dorso-ventral patterning relies on 2 different proteins
- Dorsally - the Bone Morphogenetic Proteins (BMPs)
- Ventrally - SHH (sonic hedgehog protein) secreted by the notochord
Which cells can adult neural stem cells form?
- Neurones
- Oligodendrocytes
- Astrocytes
Where are the 2 sites where adult neural stem cells are often found?
- SGZ (sub-granular zone) at the dentate gyrus of the hippocampus
- SVZ (sub-ventricular zone) lateral to the ventricles
Which 2 sites do adult neural stem cells tend to migrate to?
Therefore, what functional properties might this confer?
- Hippocampus - directly from the (SGZ) dentate gyrus of the hippocampus
- Olfactory bulb - along the rostral migratory stream from adult neural stem cells migrating from the SVZ
- Memory adapation
- Meidating the therapeutic effects of some drugs e.g. anti-depressants
What is Anencephaly, how does it occur and what is the prognosis?
- Anencephaly = failure of fusion of the anterior / rostral neuropore
- The cerebral vesicles fail to develop, so there is no brain formation
- Foetuses with anencephaly tend to be spontaneoulsy aborted
What is Spina Bifida?
What is the most common form of Spina Bifida?
- Neuralation defect commonly affecting the posterior / caudal neuropore
- However, this doesn’t mean that defects are only very caudal anatomically
- Spina Bifida Occulta is the most common form of Spina Bifida
What is Spina Bifida Occulta?
What is the prognosis and how does it depend on the anatomical location?
- Spina Bifida Occulta = failure of fusion of the dorsal parts of the lower vertebrae
- Defects in the meninges and neural tissue may herniate through the defect resulting in meningocoele or myelomeningocoeles
- When the bony defect occurs at the base of hte skull, the meningocoele can be more safely excised with accruing as much neurological damage ,whereas if it occurs in the lower spinal cord, it often would cause much greater neurological deficit
What disease of the CNS is Spina Bifida associated with?
- Hydrocephalus
What is cortical dysplasia and how does it occur and what disease it often implicated in?
- Cortical dysplasia = abnormal migration of developing cortical neurones
- Implicated in epilepsy
