How To Make a Brain Flashcards
What does the neural tube form from? and what is this process called?
- The neural plate
* Neurulation
What is the neural plate formed from?
Columnar epithelium (neuroectoderm)
What happens at day 19
A midline groove becomes apparent
What is neurulation induced by?
The notocord
What happens at day 20-21?
The edge of the plate thickens, forming the neural fold and neural groove
When do the edges of the neural fold roll over and what causes this to happen?
In the 4th week, actin contracts (apical constriction)
When does the rostral end of the neural tube close?
Day 25
When does the caudal end of the neural tube close?
Day 27
What happens if the rostral end of the neural tube fails to close?
- Causes Anencephaly
- Infants are born without a forebrain
- Usually unreactive to light and sound
- Usually stillborn
- Some may exhibit respiration and respond to touch and sound
- 0.5-1 per 1000 live births
What are the risk factors for anencephaly?
- Folate deficiency
- Previous anencephaly
- Diabetes
- Epilepsy drugs
What is caused by defects at the caudal neuropore?
Spina bifida
What are the different types of spina bifida?
• Spina bifida occulta - 1/10 - most mild form, often pinched but not closed • Meningocele - subarachnoid space protrudes • Meningomyelocele - subarachnoid space and the spinal cord protrude • Myeloschisis - most severe form
What is a disease marker for neural tube defects?
Alpha fetoprotein
What are the swellings of the neural tube and what do they become?
- Prosencephalon (forebrain)
- Mesencephalon (midbrain)
- Rhombencephalon (hindbrain)
Describe the development of the forebrain
- Grows 2 lateral expansions connected to a central like split
- Forms the lateral ventricles and the third ventricle
Describe the development of the midbrain
- Grows slower than the forebrain, remains as a single central tube
- Forms the cerebral aqueduct
Describe the development of the hindbrain
- Develops into the (rest of) the brainstem and cerebellum with a central ventricle expanding
- Forms the 4th ventricle
What is the lateral fissure formed by?
The growth of the temporal lobe
What covers the insula?
The operculum of each cortex from each adjacent lobe
Corpus callosum
Huge hemisphere connection
Fornix
Connects the hippocampus to anterior structures
Hippocampus
memory function
Interventricular foramen
Fluid filled space connects the lateral ventricles to the third ventricle
What are the basal ganglia split by and what does this form?
Split by ascending and descending white matter bundles (internal capsule) and this forms the caudate nucleus and the lentiform nucleus
What is significant about the roof of the 4th ventricle?
It is closed then opens out, it has cells that produce cerebrospinal fluid (CSF)
Where does the cerebellum develop?
In the dorsal wall of the neural tube (wall of the IV ventricle)
What becomes the spinal cord?
Caudal neural tube
What are the layers of the caudal neural tube?
• Innermost = Ventricular layer
- progenitor cells (neurones/glia)
• Mantle layer
- neuron bodies/glia
• Marginal layer = outermost layer
- processes of neurones
What is the default for the differentiation of ectoderm?
to differentiate into nerve cells
What inhibits neural ectoderm?
Bone morphogenetic protein (BMP) inhibits neural ectoderm promoting skin
How does the notocord induce neural tube formation and nerve cell specialisation?
It produces noggin, chordin and follistatin which inhibits BMP allowing the default of neural differentiation of ectoderm to occur
What cell types do specialised cells from the neural crest give rise to?
- Skull (bone)
- Sensory and autonomic NS
- Pigment cells
Where do cells from the neural crest migrate to?
The mesoderm
What cells are produced from neural crest?
- Cranial nerve ganglia
- Dorsal root ganglia
- Autonomic ganglia
- Adrenal medulla
- Smooth muscle of cardiac outflow
- Schwann cells
- odontoblasts
- Melanocytes
- Craniofacial skeleton
- Thyroid parafollicular cells
What is Waardenburg’s syndrome?
Defective neural crest development syndrome • Autosomal dominant • Pigment abnormalities • Deafness • Constipation (Autonomic NS) • Heterochromia of the eye • Telecanthus of the eye • Some have a PAX 3 deletion
What is Treacher Collins Syndrome?
- Autosomal dominant
- Defective protein: treacle (TC0F1)
- Failure/ apoptosis of neural crest cells
- Abnormal eye shape
- Micrognathia
- Conductive hearing loss
- Undeveloped zygoma
- Malformed ears
