Development of the nervous system

Question 1

What is the first thing that happens in the early stages of CNS development

Answer 1

You get a proliferation of the ectoderm in the dorsal midline of the embryonic disc- this is called the neural plate

Question 2

What happens after the neural plate is created

Answer 2

It thickens and starts to fold up on both sides

Question 3

What happens next after the neural plate has started to fold up and thus what is the neural canal

Answer 3

The two neural folds eventually fuse together dorsally to form a tube, the neural canal is the space in the middle of the tube

Question 4

What are neural crests

Answer 4

A little bunch of cells at the tip of the neural fold- they separate from the neural folds and don’t take part in the fusion

Question 5

The neural tube and crest are sources of two different types of nervous tissue, which ones are responsible for which?

Answer 5

Neural tube= all CNS cells

Neural crests= all PNS cells

Question 6

What is neuroepithelium

Answer 6

Wall of the neural tube

Question 7

What three types of cell come from neuroepithelium and what are they?

Answer 7

Neuroblasts- All neurones that have their cell bodies within the CNS
Glioblasts- these become neuroglia (astrocytes and oligodendrocytes)
Ependymal cells- Lining of ventricles and central canals

Question 8

What cells are formed by differentiation of neural crest cells

Answer 8

Sensory neurones of dorsal root ganglia and cranial ganglia

Question 9

Initially, in proliferation of neuroepithelium, cells are attached to both the inner and outer membrane, what is the first step of differentiation after this?

Answer 9

Cells withdraw from the outer membrane towards the inner membrane and go through mitosis

Question 10

One of the daughter cells will stay attached to the inner membrane and go through the cell cycle again, what happens to the other daughter cell?

Answer 10

It migrates away from the inner membrane and develops into neuroblasts. The neuroblasts will develop processes which will then develop into axons. Eventually you will have three layers: White matter (axons), grey matter and ependymal layer

Question 11

What controls this process of differentiation and migration

Answer 11

Signalling molecules

Question 12

Where do signalling molecules come from and what do they interact with

Answer 12

They are secreted either from tissues surrounding the developing neural tube or sometimes from cells within the neural tube and they interact with receptors on the developing neuroblasts

Question 13

What else do signalling molecules guide?

Answer 13

The developing axons- they can cause either attraction or repulsion and the response depends on the concentration gradient

Question 14

What are the two key factors to do with signalling molecules

Answer 14

Concentration and timing

Question 15

What are two significant features later in development

Answer 15

The neural canal is smaller compared to thickness of wall
The grey matter has split into two different types:
Alar plate- dorsal
Basal plate- ventral

Question 16

What is the difference between the alar and basal plates

Answer 16

Alar- interneurons are becoming specialised to receive sensory information and the information comes from the developing dorsal root ganglia that have developed from the neural ganglia
Basal- Some interneurons and development of motor neurones

Question 17

What happens to the neural canal, basal plates and alar plates in a developed spinal cord

Answer 17

The neural canal becomes the central canal carrying CSF and the basal plate develops into ventral horns and alar plate develops into dorsal horns

Question 18

What is the notochord and where is it found?

Answer 18

It is found just below the basal plate in the developing neural tube. It produces several signalling molecules and concentration gradient is established with the highest concentrations near the notochord. The cells within the neural tube that are closest to the source are induced to become motor neurones

Question 19

What do other signalling molecules produced by the ectoderm do?

Answer 19

They establish a conc gradient and tend to inhibit differentiation of cells into motor neurones

Question 20

What does the brain develop from

Answer 20

The most anterior part of the neural tube

Question 21

What are the three primary vesicles that the wall of the anterior neural tube differentiates into after 4 weeks?

Answer 21

Prosencephalon- future forebrain
Mesencephalon- future midbrain
Rhombencephalon- future hindbrain
The rest becomes the spinal cord

Question 22

What happens over the next week after the differentiation of the wall of the anterior neural tube ?

Answer 22

The most anterior vesicle divides in two and third vesicle also divides in two to produce 5 secondary vesicles:
Telencephalon
Diencephalon
Midbrain
Pons
Medulla

Question 23

What does the telencephalon become when it expands enormously?

Answer 23

The cerebral hemispheres

Question 24

As development continues, you get more growth of the wall of the neural tube and the space within it has become smaller, what does this space become?

Answer 24

The ventricular system

Question 25

Where does the cerebellum develop from

Answer 25

The back of the pons

Question 26

As the vesicles aren’t in a straight line, there are three flexures, what are they called?

Answer 26

Cephalic flexure, pontine flexure and cervical flexure. As you go through development they become exaggerated

Question 27

What happens with the telencephalon at 8 weeks

Answer 27

It has become so big it begins to move back and cover the diencephalon

Question 28

What is the first thing that happens in the region that becomes the brainstem

Answer 28

The development of the 4th ventricle

Question 29

What sort of matter makes up the core of the brain

Answer 29

White matter, grey matter is around the outside