Development of the nervous system

Question 1

Describe the early development of the nervous system.

Which are the three layers of the embryo?

Answer 1

1. Proliferation and thickening of ectoderm in the dorsal midline of embryonic disc is the neural plate.
2. Neural plate folds to become the neural canal/tube, which contains neuroepithelium. Neuroepithelium develops into CNS.
3. Neural crest (bunch of cells at tip of neural fold) develops into PNS.

3 layers: endoderm, mesoderm, ectoderm

Question 2

LO1 What can go wrong in normal development?

Answer 2

genetic mutation and environmental factors such as the mother’s lifestyle, diet and teratogens (substances that can affect the embryo in utero (alcohol particularly, deficits in folic acid lead to spina bifida and anencephaly)

Question 3

LO1 Describe the 3 types of cells that come from the differentiation of neuroepithelium

Answer 3

1. Neuroblasts: all neurons with cell bodies in CNS

2. Glioblasts: (will become neuroglia: astrocytes and oligodendrocytes)

• astrocytes: multifunctional, contribute to blood brain barrier - oligodendrocytes: glial cells, central myelinating cells of sns

3. Ependymal cells: lining ventricles and central acanal

Question 4

LO2 Describe the 4 types of cells that come from the differentiation of neural crest cells

Answer 4

1. Sensory neurones of dorsal root ganglia
2. Postganglionic autonimic neurones
3. Schwann cells
4. Non-neuronal derivatives e.g. melanocytes
   note: neural crest develops lateral to neuroepithelium

Question 5

Proliferation of Neuroepithelium

Answer 5

bottom cells are actively dividing (mitosis)

Question 6

Describe the proliferation and differentiation of Neuroepithelium - Formation of 3 layers of the neural tube

Answer 6

Proliferation:

fat cells at the bottom are undergoing mitosis

Differentiation:

1. Neuroblast migration:
   - Cells move towards inner membrane of neural tube
   - On inner membrane: undergoes mitosis
2. Daughter cell 1: becomes ependymal matter
   - Remain on inner membrane
   - Undergoes mitosis again
3. Daughter cell 2: becomes grey matter and white matter axons
   - Migrates towards outer membrane
   - Develops into neuroblast
   - Processes, destined to become axons, start to form = directed towards outer membrane
4. Repetition of this process -> formation of 3 layers that form basis of grey and white matter
5. Glioblasts: become grey and white matter
   - Undergo a similar process to neuroblasts – differences are:
   - Also migrate all the way out into the white matter
   - Do not develop any processes

laz’s flashcards

Firstly, you get cells withdrawing away from the outer membrane towards the inner membrane where it undergoes mitosis
One of the daughter cells will remain attached to the inner membrane and the other daughter cell will move away from the inner membraneand become a neuroblast
The neuroblast will develop processes and one will become the axon
These axons are directed away from the inner membrane
Three layers are formed: ependymal, grey matter and white matter

Question 7

What controls differentiation of neuroepithelium?

Answer 7

1. Signalling molecules, secreted by surrounding tissues, interact with receptors on neuroblasts
2. control migration and axonal growth by attraction and repulsion
3. depends on concentration gradient and timing

Question 8

LO4 Label the diagram of the developing spinal cord, naming the type of neurones/ cells in each area.

Answer 8

Notes: neural canal is even smaller compared to thickness of wall, grey matter has split into alar plate (dorsal) and basal plate (ventral)

Question 9

Describe the development of the brain at

a) approx 4 weeks
b) appx 5weeks
c) approx 8 weeks using diagrams

Answer 9

a) diffrentiation of the wall of anterior neural tibeto form three primary vesicles:
- prosencephalon
- mesencephalon
- rhomboncephalon
- rest becomes spinal cord
b) the most anterior vesicle divides in two and the third vesicle also divides in two producing 5 secondary vesicles

Question 10

Describe the folding of the development of the brain at

a) approx 4 weeks
b) appx 5weeks c) approx 8 weeks using diagrams

Answer 10

Vesicles are in three flexures.

Question 11

Summarise how cerebral cortical layers form the neuroepithelium

Answer 11

• Grey matter consists of nuclei that have migrated from the inner membrane of the neural tube
• Neuroblasts proliferate near the inner membrane. some will stay in the middle to form the basal ganglia.
• Neurones that migrate towards outer membrane (by attaching themselves to radial glial cells) have their cells bodies anchored in the inner membrane and have a single long process that goes to the outer membrane.
• Neuroblasts attach themselves to radial glial cells and climb up towars the outer membrane. wave of proliferation near the inner membrane and then a wave of migration towards the other surfaceand then one layer of t… 6 layers

Question 12

Summarise the separation of the grey matter into sensory and motor areas.

Answer 12

The grey matter (neural tube) later splits into:

1. Alar Plate:
   - Composed of interneurons
   - Will receive sensory input from dorsal root ganglia
2. Basal Plate:
   - Composed of motor and interneurons – will have a

motor function

Question 13

The mature spinal cord. Label the diagram below.

Answer 13

Final mature spinal cord is produced from development of both neural tube and neural crest.

Neural canal becomes central canal alar plates become dorsal horns basal plates become ventral horns

Question 14

What does normal development depend on?

Answer 14

coordinated completion of several complex process:

• proliferation
• differentiation
• migration
• axon growth
• synapse formation

Question 15

LO5 Developmental biology: explain how an understandinf of developmental neurobiology may help in the treatment of neurobiological disorders