W19-L6: Development of the CNS

Question 1

In what direction does the neural tube develop

Answer 1

Rostral to caudal

Question 2

How many events of neural fold closure are there and which one does folate protect against?

Answer 2

5, each which can independently go wrong. Folate protects against stage 5 which is called spina bifida

Question 3

Segmentation of neural tube

Answer 3

Rostral end of neural tube starts to swell and forms 3 distinct vesicles:
• Prosencephalon (forebrain)
• Mesencephalon (midbrain)
• Rhombencephalon (hindbrain)

Question 4

Further segmentation of neural tube after 3 swellings

Answer 4

Prosencephalon splits - telencephalon and diencephalon

• Rombencelphalon – 7 segments

Question 5

Neural crest cells

Answer 5

Cells at top of the neural tube form the neural crest, which migrate away from the neural tube to form a wide range of structures

Question 6

Neural crest derivatives

Answer 6

Peripheral nervous system, melanocytes, Muscle cartilage and bone of skull, jaws, face
and pharynx, dentine

Question 7

Neural crest migration

Answer 7

Neural crest cells follow specific paths through the embryo

Question 8

Ventricular Zone

Answer 8

All neurones are born at ventricular surface (which contains stem cells) and then migrate to outer surface to add layers

Question 9

What is the role of radial glia?

Answer 9

Neurones use radial glial cells as scaffolding to migrate across the cortex

Question 10

Developmental disorders can be caused by

Answer 10

Cortex can be malformed as a result of mutations in genes that affect migration

Question 11

Reelin mutation

Answer 11

Decreased folds and white matter due to poor migration of new neurones

Question 12

Lissencephaly

Answer 12

Smooth brain due to smaller number of cells because of mutations in neuronal migration

Question 13

Floor plate development

Answer 13

Sonic Hedgehog is released from notochord which causes the closest cells to form a floor plate which gives the direction of ventral

Question 14

Role of the floor plate

Answer 14

Induces ventral horn motor neurones by releasing sonic hedgehog

Question 15

Induction of interneurones

Answer 15

Ventral horn Motor neurones can tell interneurones they are more dorsal and they form interneurones (due to motor neurone factor)

Question 16

What is the importance of the initial scaffold of axon tracts laid down by pioneer axons?

Answer 16

Guides all the other axons later on

Question 17

Growth cone

Answer 17

A dynamic structure of cytoskeleton that is capable of crawling across a surface and pulls the axon into position

Question 18

Axon navigation

Answer 18

Growth cone responds to local cues and grows up chemical gradients

Question 19

What is the “critical period” in CNS development?

Answer 19

Refinement of synaptic connections that establishes mature functional nervous system

Question 20

If you temporarily cover one eye shortly after birth in a kitten, then test covered eye six months later…

Answer 20

the eye is blind as the visual cortex has been remodelled. 2-3 weeks after birth closing the eye has less of an effect and at 6 weeks no effect

Question 21

If you temporarily cover both eyes shortly after birth in a kitten, then test covered eyes six months later…

Answer 21

They are normal as refining connections depending on experience, if no information from one eye will choose the other, if both are covered has no information from either so cannot choose one over the other i.e no ocular dominance