Development of the Nervous System FINAL

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 and eventually the two neural folds fuse to form a tube The space in the middle is the neural canal

Question 3

What is the name given to the bunch of 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

What is the name given to the wall of the neural tube?

Answer 5

Neuroepithelium

Question 6

What three types of cells do neuroepithelium give rise to?

Answer 6

Neuroblasts – all cells with cell bodies in the CNS, this includes motor neurone and interneurons as their cell bodies are in the CNS, whereas sensory neurons do not come from neuroblasts but from the neural crest cells

Glioblasts – these become neuroglia (astrocytes + oligodendrocytes ONLY, not microglia which has a different source. Ependymal cells are a type of glial cell but they have a separate lineage outlined below)

Ependymal cells – line the ventricles and the 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 four cell types that neural crest cells can differentiate into.

Answer 8

Sensory neurons of dorsal root ganglia and cranial ganglia

Autonomic post-ganglionic neurons

Schwann cells

Non-neuronal cells e.g. melanocytes

Question 9

Describe the arrangement of the neuroepithelium.

Answer 9

Neuroepithelium has an inner layer and an outer layer Most cells are connected to both the inner and outer layer but the nuclei are at different positions

Question 10

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

Answer 10

Ependymal, grey matter and white matter AKA germinal layer, mantle layer, marginal layer

Question 11

What guides the process of differentiation?

Answer 11

Signalling molecules

Question 12

Which factors are important with regards to signalling molecules?

Secreted by, intercact with, method of control

Answer 12

Concentration and timing

Secreted by surrounding tissues, interact with receptors on neuroblasts, control migration and axonal growth by attraction and repulsion

Question 13

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

Answer 13

Alar plates and basal plates

Question 14

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

Answer 14

Alar plate – interneurons Basal plate – interneurons and motor neurons

Question 15

Around 4 weeks, you get differentiation of the wall of the anterior neural tube to form three primary vesicles. Name these primary vesicles.

Answer 15

Prosencephalon – future forebrain (prosen= leaning forwards)

Mesencephalon – future midbrain (mesen=middle)

Rhombencephalon – future hindbrain (rhombus shaped)

Question 16

Describe the changes that occur to these three vesicles in the week or so following their formation.

Answer 16

The first and third vesicles divide into two

1. Prosencephalon - telencephalon (future cerebral cortex) + diencephalon (thalamus and hypothalamus)
2. mesencephalon stays the same (becomes midbrain)
3. Rhombencephalon - pons + medulla

Question 17

What important structure begins to appear quite late in development (around 8 weeks) and where does it appear from?

Answer 17

Cerebellum – appears as an out pouching from the back of the pons

Question 18

Name the three flexures in the developing brain.

Answer 18

Cephalic Pontine(related to pons) Cervical

Question 19

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

Answer 19

Motor = medial Sensory = lateral Autonomic = in between

Question 20

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

Answer 20

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

Question 21

What happens to neuroblasts that stay in the middle of the cortex?

Answer 21

They become the basal ganglia

Question 22

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

Answer 22

SIX

Question 23

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

Answer 23

Spina bifida

Question 24

What is are teratogens

What is anencephaly

Answer 24

Agents that affect developing processes

Neural tube needs to close at both ends. Anencephaly is when the rostral end does not close and you essentially get no brain/little brain that is open and lacks a skull to protect it

anencephaly= without

Question 25

What is encephalocele

Answer 25

rostral end of neural tube doesn’t close completely causing Herniation because part of the skull in the occipital area didn’t fuse properly so contents herniate out

encephalo= brain

cele= hernia/tumour/swelling

Question 26

what is iniencephaly

Answer 26

extreme retroflexion of head ( bend back) caused by incomplete closure of the rostral end of the neural tube

from anatomy- inion is at the back of the skull on the occipital bone

Question 27

What are the four types of ntd of the base

Answer 27

1) spina bifida occulta: closed, asymptomatic NTD

some of vertebrae not completely closed

2) closed spinal dysraphism: Deficiency of at least 2 vertebral arches
3) Meningocele: Portrusion of the meninges – filled with CSF, through defect in skull or spine
4) Myelomeningocele: open spinal cord

Question 28

what is craniorachischisis

Answer 28

Craniorachischisis: most severe form of neural tube defect. This is when both ends of the neural tube do not close, causing an open and exposed brain and spinal cord (see pics online)

Cranio=brain

Rachi=spine

Schisis= split

Question 29

Where is grey and white matter located for brain

Answer 29

Grey outside

White inside