Development of the Nervous System

Question 1

What is the name given to the proliferation of the ectoderm in the dorsal midline?

Answer 1

Neural plate

Question 2

What happens to the neural plate as it thickens?

Answer 2

It folds up the sides + eventually the 2 neural folds fuse to form a tube
Space in the middle = neural canal

Question 3

What is the name given to the cells at the tip of the neural fold that are excluded in the fusion?

Answer 3

Neural crest

Question 4

Which cells do the neural tube and neural crest cells give rise to?

Answer 4

Neural tube – all cells of the CNS

Neural crest – all cells of the PNS

Question 5

Name of the wall of the neural tube

Answer 5

Neuroepithelium

Question 6

What 3 types of cells do neuroepithelium give rise to?

Answer 6

Neuroblasts: all neurones with cell bodies in the CNS
Glioblasts: Astrocytes + Oligodendrocytes
Ependymal cells: line ventricles + central canal

Question 7

Are motor neurons produced from neuroepithelium?

Answer 7

Yes – although most of their axons are outside the CNS, their cell bodies are within the spinal cord

Question 8

State 4 cell types that neural crest cells can differentiate into.

Answer 8

Sensory neurons of dorsal root ganglia
Autonomic post-ganglionic neurons
Schwann cells
Non-neuronal derivatives e.g. melanocytes

Question 9

Describe the arrangement of the neuroepithelium.

Answer 9

Neuroepithelium has an inner + outer layer
Most cells are connected to both the inner + outer layer but the nuclei are at different positions
Cells actively dividing closest to inner layer

Question 10

What are the 3 layers formed by the differentiation of the neuroepithelium?

Answer 10

Ependymal (germinal layer- lines canal) = developmental cells
Grey matter (mantle layer- where neuroblasts migrate)
White matter (marginal layer) = axons + processes of neurones

Question 11

What guides the process of differentiation and migration?

Answer 11

Signalling molecules secreted by surrounding tissues

Control migration + axonal growth by attraction + repulsion

Question 12

Which factors are important with regards to signalling molecules?

Answer 12

Concentration gradient

Timing

Question 13

What can the grey matter of the neural tube be divided into? What is their orientation?

Answer 13

Alar plates (Dorsal)
Basal plates (Ventral)

Question 14

Which types of neurons do the alar plate and basal plate give rise to?

Answer 14

Alar plate: interneurons

Basal plate: interneurons + motor neurons

Question 15

Which structures around the neural tube release signalling molecules and what effect do they have on the cells in the neural tube?

Answer 15

Notochord and ectoderm
Notochord signalling molecules: induce cells to differentiate into motor neurons
Ectoderm signalling molecules: inhibit cells from differentiating into motor neurons

Question 16

Name the 3 primary vesicles formed from the differentiation of the wall of the anterior neural tube at ~4 weeks

Answer 16

Prosencephalon: future forebrain
Mesencephalon: future midbrain
Rhombencephalon: future hindbrain

Question 17

Describe the changes that occur to the 3 vesicles in week 5

Answer 17

The 1st + 3rd vesicles divide in 2:
Prosencephalon= telencephalon + diencephalon
Rhombencephalon= pons + medulla

Question 18

What important structure begins to appear at ~ 8 weeks and where does it appear from? What else starts to arise?

Answer 18

Cerebellum
Appears as an out pouching from the back of the pons
Ventricular system starts to arise

Question 19

Name the 3 flexures in the developing brain.

Answer 19

Cephalic
Pontine
Cervical

Question 20

Describe the arrangement of motor, sensory and autonomic cranial nuclei within the brainstem.

Answer 20

Motor = medial 
Sensory = lateral 
Autonomic = in between

Question 21

How do neuroblasts migrate from the inner membrane to the outer membrane in the brain?

Answer 21

They attach themselves to radial glial cells + climb up towards the pill surface
Radial glial cells have their cell bodies anchored to the inner membrane + have a single long process to the outer membrane

Question 22

How many layers of cells are there within the cerebral cortex?

Answer 22

6

Question 23

What can a deficiency of folic acid in pregnancy lead to?

Answer 23

Spina bifida (No closure of base of neural tube)

Question 24

What is the difference in distribution of grey and white matter in the brain and spinal cord?

Answer 24

Brain: Grey matter surrounds white matter
Cord: White matter surrounds grey matter

Question 25

What gives rise to developmental disorders?

Answer 25

Genetic mutations
Environmental factors e.g. Mothers lifestyle, diet + teratogens
These interfere with the coordinated completion of the complex processes