Neuro Flashcards
Describe the formation of the neural tube
- Gastrulation produced the notochord- a solid rock of cells in the midline.
- notochord directs conversion of overlying ectoderm into neuroectoderm
- which causes elevation of the lateral edges of the neural plate and depression of the midline region of the neural groove
- The neural folds approach in midline and fuse, producing the neural tube
What is the name for the regions where the caudal (posterior) and cranial (anterior) parts of the neural tube fuse?
neuropores
What results from failure of fusion of the anterior and the posterior neuropores?
anterior: anencephaly
posterior: spina bifida
Describe the 3 types of spina bifida?
spina bifida occulta: spinious processes dont form but no herniation of spinal canal
Meningocele: hernation of dura out but spinal cord remains within normal canal boundaries
Myelomeningocele: spinal cord herniates out too. Skin may fail to form over herniated dura.
What does spina bifida cause?
Hydrocephalus as impairs CSF drainage, this leads to cognitive delay and needs shunt to drain CSF
Why does no one have anencephaly?
because it leads to absence of brain and other cranial structures so is incompatible with life.
What is rachischisis?
failure of neural fold elevation and so neural tube doesnt form so is incompatible with life.
How can neural tube defects be detected? (2)
- USS
- blood tests showing raised a- fetoprotein
How can neural tube defects be avoided?
folic acid supplementation preconceptually and in 1st trimester
Explain why we have a cauda equina, not just one long spinal cord?
By the 3rd month the spinal cord and the vertebral column are the same length and the spinal roots form, but the vertebral column keeps growing, elongating the lumbar and sacral spinal roots as it does so
Describe the initial 3 brain regions and the 5 secondary regions which form
Initially; prosencephalon (forebrain), mesencephalon (midbrain) and rhombencephalon (hindbrain)
Then: forebrain becomes telencephalon and diencephalon, midbrain stays as mesencephalon and hindbrain becomes metencephalon and myelencephalon
Describe what the 5 secondary brain regions go on to become?
- telencephalon-> cerebrum
- diencephalon-> thalamus, hypothalamus
- mesencephalon-> midbrain
- metebcephalon-> pons and cerebellum
- myelencephalon-> medulla
Describe the folding of the cranial neural tube?
it exceeds space linearly so tube folds twice; at spinal cord- hindbrain junction (cervical flexure) and at midbrain region (cephalic flexure)
describe formation of the ventricles
the tubular structures of the neural tube persist (telencephalon becomes lateral ventricles, diencephalon becomes third ventricle etc)
What is the significance of the alar and basal plates of the neural tube?
The alar plate is found dorsally and creates sensory neurones, the basal plate is found ventrally and creates motor neurones.
