Development of the Nervous System Flashcards

1
Q

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

A

Neural plate

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2
Q

What happens to the neural plate as it thickens?

A

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

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3
Q

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

A

Neural crest

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4
Q

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

A

Neural tube – all cells of the CNS

Neural crest – all cells of the PNS

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5
Q

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

A

Neuroepithelium

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6
Q

What three types of cells do neuroepithelium give rise to?

A

Neuroblasts – all cells with cell bodies in the CNS
Glioblasts – these become neuroglia (astrocytes + oligodendrocytes)
Ependymal cells – line the ventricles and the central canal

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7
Q

Are motor neurons produced from neuroepithelium?

A

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

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8
Q

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

A

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

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9
Q

Describe the arrangement of the neuroepithelium.

A

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

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10
Q

Describe the differentiation of the neuroepithelium.

A

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

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11
Q

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

A

Ependymal, grey matter and white matter

AKA germinal layer, mantle layer, marginal layer

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12
Q

Glioblasts show a similar pattern of differentiation to neuroblasts. State one difference.

A

Glioblasts can migrate into the white matter

NOTE: glioblasts do not develop axons (but they do develop processes)

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13
Q

What guides the process of differentiation and migration?

A

Signalling molecules

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14
Q

Which factors are important with regards to signalling molecules?

A

Concentration and timing

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15
Q

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

A

Alar plates and basal plates

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16
Q

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

A

Alar plate – interneurons

Basal plate – interneurons and motor neurons

17
Q

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

A

Notochord and ectoderm
Notochord releases signalling molecules that induce the cells nearest to it to differentiate into motor neurons
Ectoderm produces signalling molecules that inhibit the cells nearest to it from differentiating into motor neurons

18
Q

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

A

Prosencephalon – future forebrain
Mesencephalon – future midbrain
Rhombencephalon – future hindbrain

19
Q

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

A

The first and third vesicles divide in two
Prosencephalon -telencephalon + diencephalon
Rhombencephalon - pons + medulla

20
Q

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

A

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

21
Q

Name the three flexures in the developing brain.

A

Cephalic
Pontine
Cervical

22
Q

Describe the formation of the 4th ventricle.

A

In the neural tube in the region that will become the brainstem, the roof plate rapidly proliferates and causes the alar plates to split apart so that they are lateral to the roof plate
The space left from the proliferation of the roof plate will become the 4thventricle

23
Q

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

A
Motor = medial 
Sensory = lateral 
Autonomic = in between
24
Q

What structure divides the motor nuclei from the sensory nuclei in the brainstem?

A

Sulcus limitans

25
Q

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

A

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

26
Q

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

A

They become the basal ganglia

27
Q

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

A

SIX

28
Q

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

A

Spina bifida