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Fundamentals of neuroscience > Neurodevelopment (anatomy) > Flashcards

Neurodevelopment (anatomy) Flashcards

1
Q

Why is it so important that the brain devleops properly?

A

The brian is made up of:
- Neurones = 10^11 (100bn)
- Glial cells = 10^12
- Synapses = 10^14

Thereofre it is very complex w lots of networks so is important it devleops right

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2
Q

What are the 2 divisions of development of the nervous system?

A
  1. Anatomical development
  2. Cellular development
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3
Q

What happens during anatomical devleopment of the NS?

A
  • Formation of the neural tube
  • Neural crest cells
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4
Q

What happens during cellular devlopment of the NS?

A
  • Generation of new cells
  • Migration of cells
  • Making connections
  • Death of cells
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5
Q

What happens when sperm fertilises the egg?

A

There is a massive cell division that occurs

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6
Q

What happens around 11-15 days in the embryo?

A

At this point it consists of the 3 important layers for development:
- Endoderm
- Mesoderm
- Ectoderm

These 3 layers go on to form all the different organs of the body

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7
Q

What does the endoderm go on to form?

A

Form the cells that line our internal organs

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8
Q

What does the mesoderm go on to form?

A

Muscle, bone & the immune system

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9
Q

What does the ectoderm go on to form?

A

The NS - also the epidermis

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10
Q

What are the 3 main stages in neurulation?

A
  1. Formation of the neural plate
  2. Formation of the neural folds & neural groove
  3. Closure of neural folds forming neural tube & migration of neural crest cells
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11
Q

What is neurulation?

A

The formation of the neural tube from the notochord

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12
Q

What is the entire process of forming the neural tube?

A
  • During neurulation the notochord (part of mesoderm) starts to send out signals
  • Signals form notochord stimulate the differentiation of the cells of the neuroectoderm into the NEURAL PLATE (an elongated sheet of cells)
  • As development continues, the neural plats starts to fold in on itself - creates NEURAL GROOVE
  • Neural folds are on the side of the groove, they fuse to the top to form the neural tube –> will go on to form the anatomicla part of the CNS
  • Few cells at the tips of the neural folds called the neural crest cells don’t form into the tube & leave –> migrate to form the PNS
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13
Q

What do the cells on top of the neural tube form?

A

On top we get the remaining ectoderm which will formt the epidermis (skin)

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14
Q

How does the neural tube join up?

A

It doesn’t happen simultaneously all the way along

The join starts at the neck region & will progress rostrally (up to brain) and caudally (spinal cord) to close the structure

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15
Q

What do the anterior (rostral) and posterior (caudal) ends of the neural tube form?

A

Anterior = brain

Posterior = spinal cord

Fuses halfway between the brain and moves either way to properly join the neural tube

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16
Q

What happens to the anterior part of the neural tube before 4 weeks?

A

(The brain)

We get further differentiation from it being a tube structure

It differentiates into swelling (vesicles) & this is what forms the anatomical divisions of the brain & give it its structure

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17
Q

What happens to the posterior part of the neural tube at 4 & 6 weeks?

A

(Spinal cord)

Posterior pretty much remains the same

It is a tube structure which makes sense as it goes on to form the spinal cord which appears as a long tube

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18
Q

What happens to the anterior part of the neural tube between 4-6 weeks?

A

(Forming the brain)

Around 4 weeks = Differentiates into 3 parts; forebrain, midbrain & hindbrain

6 weeks = development cont. –> we get furhter differentiation of the fprebrain vesicles

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19
Q

What are the further vesicular divisions of the forebrain at 6 weeks?

A
  • Telencephalic vesicles
  • Diencephalon
  • Optic vesicles
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20
Q

What do the telencephalic vesicles turn into?

A

Cerebral hemispheres

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21
Q

What does the diencephalon turn into?

A

Thalamus & hypothalamus

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22
Q

What do the optic vesicles turn into?

A

Optic nerve & retinal (eye)

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23
Q

Why are the optic nerves and olfactory bulb considered more CNS than PNS compared to other cranial nerves?

A

They sproud directly from the brain tissue, os they are jsut an extension of this –> making them more CNS

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24
Q

After 6 weeks how does the shape of the brain change?

A

As developemnt goes further, the cerebral hemispheres swell both POSTERIORLY (backwards) & LATERALLY (around the side of the brain)

This envelopes the diencephalon

We get a sprouting of olfactory bulbs from the ventral side as well

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25
Q

After the diencephalon forms the thalamus & hypothalamus what happens to it?

A

It ends up just touching the sub hemisphere of the brain once it’s fully developed

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26
Q

What happens to the neural crest cells that do not form the neural tube?

A

They migrate away to form:

  • The PNS
  • The enteric NS
  • Cells of the skin (melanocytes)
  • Parts of the skull
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27
Q

What are the 2 neural tube defect diseases?

A
  • Spina bifidia
  • Anecephaly
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28
Q

What is spina bifidia?

A
  • Failure of neural tube in the spinal cord to fuse
  • Most common in lower back = lumbosacral region
  • Paralysis below this region
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29
Q

What is anencephaly?

A
  • Failure of neural tube in brain region to fuse
  • Incompatible with postnatal survival
30
Q

What is the treatment for neural tube defects?

A

Folate supplement for pregnant women –> mechanism unclear

31
Q

What happens if the neural crest cells fail to migrate?

A

Causes Hirschsprug’s disease

32
Q

What is Hirschsprung’s disease?

A
  • Failure of neural crest cells to migrate to large intestine (colon)
  • No autonomic NS innervation of the large intestine
  • Means no peristalsis at a point in the gut - no movement of contents, causes build up
  • Constipation
33
Q

What is the treatment for Hirschsprung’s disease?

A

Surgery to bypass or remove diseased part of the colon

34
Q

What does the lumen of the neural tube form?

A

Forms brain ventricles - where CSF flows through

35
Q

What is the subventricular zone?

A
  • Region adjacent to the lumen of the neural tube
  • Contains neural stem cells = neuroepithelial cells
  • Produces neurones & glial cells (divide via mitosis)
36
Q

What are the 3 types of neurones?

A
  • Sensory
  • Motor
  • Inter
37
Q

How is it determined what type of neurone it will become?

A

It is determined by their exposure to different proteins at different concentrations when being formed in the subventricular zone of the neural tube

38
Q

What are the 2 important proteins involved in determining what type of neurone a neurone becomes?

A
  • Bone Morphogenic Protein (BMP)
  • Sonic Hedgehog (SHH) protein

The conc of these in each area of the tube determines the type of neurone

39
Q

What sort of neurones are made in the dorsal vs ventral area of the neural tube?

A

Dorsal = makes sensory

Ventral = makes motor

40
Q

Which cells in the neural tube produce Bone Morphogenic Protein (BMP)?

A

Cells on the roof plate (dorsal) of the neural tube (make sensory neurones)

Once produced diffuses down the side of the neural tube

41
Q

Which cells in the neural tube produces Sonic Hedgehog (SHH) protein?

A

Cells in the floor plate (ventral) of the neural tube (makes motor neurones)

Once produces can diffuse thru neural tube

42
Q

Where in the neural tube are interneurones produced?

A

In the middle, they are produced around the hlaf way point where the hormones SHH and BMP diffuse close enough

43
Q

What are the two things that can go wrong with neurone production?

A

Reduced cell proliferation caused by environmental insults

OR

Uncontrolled cell proliferation

(So it is important that the production of the cells is controlled & regulated to prevent these)

44
Q

What can reduced cell proliferation caused by environmental insults cause?

A
  • Toxins e.g. sodium valproate
  • Infections agents e.g. rubella
  • Undernutrition
  • Maternal inflammation
  • Neurodevelopmental disorders e.g. autism, schizophrenia
45
Q

What can uncontrolled cell proliferation cause?

A

Childhood brain cancer

46
Q

What is symmetrical division?

A

1 radial glial cell —> divides into 2 glial cells

47
Q

What is asymmetrical division?

A

1 radial glial cell –> divides into 1 radial glial cell & 1 neuron

48
Q

How are neurones produced from a glial cell?

A
  • Neuroepithelial cells divide, they differentiate into radial glial cells
  • Radial glial cells can divide, initially symetrically into 2 glial cells
  • Eventually their division becomes asymmetrical & produce a glial cell & a neurone
  • Fate is determines by hormones BMP and SHH
49
Q

What do the glial cells produced by symmetrical division turn into?

A
  • Can differentiate into other glial cells e.g. astrocytes

OR

  • They can act as scaffolding for neurones to grow
50
Q

How can glial cells act as scaffolding for neurones?

A

They have rlly long processors from the subventricular zone all the way to the top of the brain

Neurones produced during this division can use the scaffolding & migrate to other areas in the brain

51
Q

How many layers doe the cortex have & how are they structured?

A

6 layers - formed from the bottom upwards

Outer layer = 1
Innermost layer = 6

52
Q

Where in the brain is migration of neurones particularly important?

A

The cortex, as it has many layers which are carefully arranged

Migration allows the neurones to get to the correct layer

53
Q

What can cause improper formation of the cerebral cortex?

A

failure of cell migration

54
Q

What can failure of cell migration in the cerebral cortex lead to?

A
  • Incorrect layering
  • Which can cause some types of epilepsy
55
Q

What are neurites?

A

Processors that neurones send out for growth

Have growth cones on the end of these

56
Q

What is the growth cone?

A

Found on the end of neurites

They are able to move thru the extracellular environment & navigate towards its target neurone

Extends the neurite behind it

57
Q

What allows the growth cone to move?

A

Protein-protein interactions

Proteins expressed on the growth cone:
- Laminin of the extracellular matrix
- Integrins expressed by growth cone

58
Q

What attracts the growth cone to its target?

A

Guidance cues

Different growth cones express different detectors of different guidance cues

59
Q

What are the types of guidance cues?

A
  • Chemoattractant
  • Chemorepellent
60
Q

What happens once the growth cone reaches its target?

A

A synapse is formed

61
Q

What are the 2 main methods of cell death?

A
  • Competition for tophic factors
  • Synaptic rearrangement
62
Q

What are the 2 main trophic factors that neurones are in competition for?

A
  • Nerve Growth Factor (NGF)
  • Brain Derived Neurotrophic Factor (BDNF)
63
Q

What is the action of trophic factors?

A

They are released from postsynaptic neurones & bind to receptors on presynaptic neurone

64
Q

How do trophic factors help cells?

A

They inhibit programmed cell death (apoptosis)

65
Q

How are trophic factors used to control the amount of neurones?

A

We produce a lot more neurones in the brain than we need –> excess need to be removed via apoptosis

Competition for trophic factors is high –> those which cannot get them will go through apoptosis

66
Q

What happens during synaptic rearrangement?

A
  • It refines synaptic connections
  • Those that are active have more connections –> those who are less active will have their connections cut
67
Q

When does synpatic rearrangment happen most?

A

During childhood

This is why early childhood experiences are so important as they determine which connections are cut

68
Q

When is the production of glial cells at its most?

A

In the first 2 years

69
Q

When does formation of synapses peak?

A

At 2 years –> when 2,000,000 new synapses per second are forming

70
Q

How long does mylenation happen for?

A

Continues into your 20s and 30s

This is the oligodendrocytes essetially generating the optimum conduction velocity

71
Q

How can extreme neglect at a young age affect brain development?

A

It can have a severe effect on neurodevelopment as it is essentially changing the structure of the brain

(Key stage in glial formation & synapse formation happens in the first 2 years)

Fundamentals of neuroscience (38 decks)

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