Development of the brain, brain injury and neuroprotection

Question 1

What are the 6 stages of neural development?

Answer 1

1. Neurulation
2. Proliferation
3. Migration
4. Differentiation
5. Axon growth and synaptogenesis
6. apoptosis
7. myelination

Question 2

What occurs during neurulation?

Answer 2

Begins at week 3

1. ectoderm thickens forming neural plate
2. plate folds inwards forming neural groove
3. sides of neural grove come together and fuse on top closing neural groove forming neural tube
   - this tube will become the brain and spinal cord
4. neural tube then bulges and bends and at week 4 there are primary vesicles in this tube
   a. prosencephalon forms cerebrum
   b. mesencephalon form midbrain
   c. rhombencephalon forms brainstem and cerebellum
   d. end of neural tube forms spinal cord
5. Neural tube continues to develop, two vesicles further divide to form secondary vesicles
   a. prosencephalon:
   - telencephalon (cerebral hemispheres)
   - diencephalon (thalamus and hypothalamus)
   b. rhombencephalon
   - metencephalon (pons and cerebellum)
   - myelencephalon (medulla)

Question 3

What is the proliferation phase of neural development

Answer 3

1. inter-kinetic nuclear migration
   - neural epithelial cells positioned at bottom part of ventricle and then moves towards top part of ventricle (marginal zone)
   - where they divide into two progenitor cells then go back down
   - this creates more and more progenitor at the bottom (ventricular zone) making it larger and thicker

Question 4

What is the proliferation/ migration phase of neural development

Answer 4

2. progenitor cells in ventricle zones (called radial glial cells) switch from symmetrical and asymmetrical division
3. in asymmetrical division:
   radial glial cells divide into another radial glial cell and one post-mitotic neuron or an intermediate progenitor cell
4. radial glial cells are categorised into apical and basal
   - apical stays in the ventricle
   - basal move away and create the sub-ventricular zone
5. ventricle and sub-ventriuclar zones forms a proliferative zone where pyramidal neurons
   - these cells travel along radial glial cells which act as scaffolds for neurons to move along and form 6 layer structure in cortex
6. once migration occurs radial glial cells eventually dissapaear and become astrocytes

Question 5

What occurs during differentiation stage

Answer 5

cells become neurons or glial cells

Question 6

What are the types of glial cells and their roles

Answer 6

ependymal cells
- line ventricles
- create and secrete CSF (which provides protection and nourishment)

Microglia
- specialised macrophages (shows injury has taken place)

oligodendrocyte
- form and maintain myelin sheath
- aid nerve conduction (through insulation)

astrocyte
- transfer nutrients from circulation
-produce growth factors
- form glial scars after injury
- can become reactive if there is injury

Question 7

During the maturation of oligodendrocytes one of the precursors are pre OL cells. Injuries to pre OL by oxidative stress and hypoxia-ischemia contributes to what injury?

Answer 7

contributes to the pathogenesis of periventriucalr white matter injury
- seen in premature infants

Question 8

What occurs during the axonal growth stage of development?

Answer 8

1. growth cone in axons enables axons to react guidance proteins
2. proteins at growth cone surface binds to guidance cues inducing axon steering to predetermined routes
3. when axonal growth cones reach target region the halt and make synapses

Question 9

What are the guidance proteins used during axonal growth stage of development?

Answer 9

• semaphorins
• netrins
• slits
• repulsuve guidance molecules
• ephrins