Development of the Nervous System Flashcards
Over what time frame does the nervous system undergo development?
It is the first system to begin development, and the last to complete development
What does the early development of the nervous system reflect?
The fact that its formation is a priority for the embryo
What is meant by the nervous system being a very plastic system?
It is changing all the time, even after birth
What is the clinical relevance of the length of time it takes the nervous system to develop?
It is most susceptible to insult during pre-natal development
What effect does alcohol have on the developing nervous system?
It disrupts communication between developing neurones
What is the notocord?
A solid cord of cells
What is the notocord formed by?
Prenotocordal cells migrating through the primitive pit
What does the definitive notocord serve as?
The baseline for the midline, axial skeleton, and neural tube
What does the notocord release?
Lots of diffusion limited signalling molecules
What can the signalling molecules released by the notocord act on?
Only cells that are close, and have the right receptor
What is the result of interaction between the notocord and ectoderm?
Formation of neuroectoderm
What does the formation of neuroectoderm cause?
The induction of the neural plate
What happens to the neural plate in development?
The lateral edges of the neural plate elevate, and the depressed midregion becomes the neural groove
What happens to the neural folds during development?
They gradually approach each other in the midline and fuse
Where does fusion of the neural folds begin?
In the future cervical region (in the middle), and then proceeds in both cranial and caudal directions
What is produced by fusion of the neural folds?
The neural tube
By what stage in development is the neural tube completely closed?
Day 28-32
What do neural tube defects result from?
The failure of the neural tube to close
What happens if failure of the neural tube to close occurs caudally?
Gives spina bifida
Where in the spinal cord does spina bifida occur?
Can occur anywhere along the length, but most common in the lumbosacral region
What occurs with spina bifida?
- Neurological defects
- Hydrocephalus nearly always
Are the neurological defects in spina bifida associated with cognitive delay?
No
What is hydrocephalus?
Accumulation of the CSF within the ventricular system
What can hydrocephalus lead to?
- Brain impairments
- Congitive delay
What happens if failure of the neural tube to close occurs cranially?
Anencephaly
What is anencephaly?
Failure of formation of the head structures, including brain
What is the prognosis of anencephaly?
It is incompatible with life
What is the most severe form of anencephaly?
Rachischisis
What is rachischisis?
Failure of neural fold elevation
How can neural tube defects be deteted?
- Raised maternal serum alpha-fetoprotein
- USS
What causes neural tube defects?
Multi-factoral aetiology