neuro

Question 1

outline the embryological formation of the neural tube

Answer 1

-ectoderm thickens in midline to form neural plate
-notochord forms from mesoderm cells soon after gastrulation finishes
-signals from notochord cause inward folding of ectoderm at neural plate
ends of neural plate fuse and disconnect to form autonomous neural tube
-until end of week 4 where neural tube closes

Question 2

what do migrating neural crest cells form and where do they form?

Answer 2

• melanocytes, Schwann cells and neurons forming in ectoderm
• osteoblasts, osteoclasts, adipocytes and chondrocytes forming in mesoderm
• also form sensory root ganglia of spinal and V/VII/IX/X
• adrenal medulla
• bony skull
• meninges
• dermis

Question 3

when does neural tube usually close?

Answer 3

end of 4th week

Question 4

what results in anencephaly?

Answer 4

failure of neural tube to close at cephalic region

Question 5

what results in spina bifida?

Answer 5

failure of neural tube to close at spinal region

Question 6

what are the different prevalences for neural tube defects?

Answer 6

• general population: 1/1000
• 1 sibling has it: 1/50
• 2 siblings have it: 1/10
• parent has it: 1/25

Question 7

what are environmental factors for neural tube defects?

Answer 7

• folic acid deficiency

- maternal diabetes

Question 8

what three primary brain vesicles can be identified at the end of the 5th week of embryological development?

Answer 8

• prosencephalon: forebrain
• mesencephalon: midbrain
• rhombencephalon: hindbrain

Question 9

what differentiation occurs at the end of the 7th week, resulting in the formation of the secondary brain vesicles?

Answer 9

Prosencephalon:
-Telecephalon - thalamus, hypothalamus (including optic nerves)
-Diencephalon - grey matter in middle of brain 
Mesencephalon
-Mesencephalon
Rhombencephalon 
-Metencephalon
-Myelencephalon

Question 10

how do the secondary brain vesicles give rise to derivatives in the mature brain?

Answer 10

Prosencephalon
-Telencephalon: cerebral hemispheres, lateral ventricles
-Diencephalon: thalamus, hypothalamus, 3rd ventricle
Mesencephalon
-Mesencephalon: midbrain (tectum, tegmentum, crus cerebri), aqueduct
Rhombencephalon
-Metencephalon: cerebellum, pons, upper 4th ventricle
-Myelencephalon: medulla oblongata, lower 4th ventricle

Question 11

what is CSF and what does it do?

Answer 11

-produced as filtrate of blood at choroid plexuses in ventricles (around 120mls)
-circulates through subarachnoid spaces through ventricles
-cushions brain and helps circulate metabolites
absorbed via arachnoid granulations in superior sagittal sinus