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MedST IB: Neurobiology and Human Behaviour (NHB) > 7.0 Brain Development and Repair > Flashcards

7.0 Brain Development and Repair Flashcards

1
Q

What germ layer is neural plate from?

A

Ectoderm

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2
Q

What does neural tube become?

A

CNS

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3
Q

Where do neural crest cells come from?

A

Edges of neural tube (neural folds)

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4
Q

What do crest cells become?

A

PNS

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5
Q

Give some neural tube defects:

A

1) Spina bifida<br></br>2) Meningocele<br></br>3) Meningomyelocele

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6
Q

What establishes anterior-posterior axis?

A

HOX (homeobox) genes

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7
Q

What establishes Dorso-vental axis?

A

Sonic hedgehog (Shh)<br></br>- Induces neural tube floor plate which secretes more Shh to establish DV axis

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8
Q

What is another role of Shh?

A

Induces development of motor neurons in lower doses

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9
Q

What establishes radial axis?

A

Radial glia (provides a scaffold)

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10
Q

What do neural crest generate?

A

1) Dorsal root ganglia<br></br>2) ANS ganglia<br></br>3) ENS<br></br>4) Melanocytes<br></br>5) Schwann cells<br></br>7) Adrenal medulla (enterochromaffin cells)

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11
Q

What are the different molecules that guide axons?

A

<b>Diffusible Attractant</b><br></br>NGF<br></br>Netrin<br></br><br></br><b>Diffusible Repellent</b><br></br>Semaphorin<br></br>Slit<br></br><br></br><b>Contact Attractant</b><br></br>Cell adhesion molecules (CAMs)<br></br><br></br><b>Contact Repellent</b><br></br>Semaphorin<br></br>Ephrin<br></br>Proteoglycans

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12
Q

Role of actin in growth of axons:

A

Structural protein in the cytoskeleton of the growth cone. Provides traction for myosin

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13
Q

Role of nerve growth factor:

A

Diffusible attractant that ‘nourishes’ axon growth. Needed for survival and sprouting

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14
Q

Role of netrin:

A

Diffusible attractant that guides axon growth

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15
Q

Role of Cell adhesion molecules

A

Contact attractant that guides axon growth (connects to cytoskeleton and signal transducers in cell)

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16
Q

Role of ephrin:

A

Contact repellent that inhibits growth centres expressing its receptors and directs migrating axons away

17
Q

What events precede correct synapse formation?

A

1) Axon guidance<br></br>2) Generic synapse formation<br></br>3) Activity dependent selection to stabilise synapses

18
Q

What is the function of correlated pre- and post- synaptic activity for neural development?

A

Needed for activity dependent selection to stabilise synapses (activity dependent natural selection is dependent on LTP)

19
Q

What is Wallerian degeneration?

A

Following nerve damage - distal stump and myelin degenerate

20
Q

Steps for regeneration in PNS:

A
  1. Surviving nerve cell body reacts by re-expressing genes for axonal growth<br></br>2. Schwann cells react adaptively to promote regeneration<br></br>3. Proximal stump axons can regenerate (both motor and sensory)<br></br>• Only if a track (endoneurial tube) of living Schwann cell is present to guide them<br></br>• Following a complete break >1cm → axons merely form a neuroma (a local swelling)<br></br>• Neuroma can cause severe pain<br></br>• However if a track is present → regeneration can occur for many centimetres (albeit slowly)
21
Q

What glial cells in PNS promote axon regeneration?

A

Schwann cells

22
Q

What glial cells remyelinate axons after peripheral nerve damage?

A

Schwann cells

23
Q

What is Cajal’s Harsh Decree?

A

Axons cannot regenerate >1mm in CNS

24
Q

What glial cells in CNS inhibit axon regeneration?

A

Oligodendrocytes<br></br>Astrocytes

25
Q

What factors make adult CNS non-permissive for axon growth?

A
  1. ECM <b>lacks growth promoting molecules</b> (e.g. laminin)<br></br>2. <b>Oligodendrocytes</b> express <b>Nogo</b> (growth inhibitory)<br></br>3. <b>Astrocytes</b> produce <b>growth-inhibitory chondroitin sulphate proteoglycans (CSPGs)</b> + form <b>glial scar</b> that causes growing axons to stop
26
Q

What is a scar in the CNS called?

A

Glial scar (caused by astrocytes)

27
Q

What cells produce Nogo?

A

Oligodendrocytes

28
Q

What are possible strategies for repair of CNS?

A

“1) Block Nogo<br></br>2) Peripheral nerve graft<br></br>3) Schwann cell graft<br></br>4) Neurotrophic factors<br></br>5) Blocking inhibitory proteoglycans<br></br>6) Neural grafting (foetal cells)<div><br></br></div><div><img></img></div>”

29
Q

How does rehabilitation following nerve damage work?

A

Depends on promoting spouting of intact axons (plasticity)

30
Q

Example of ischaemic nerve injury

A

Stroke<br></br>Mechanism of injury = mainly excitotoxic → ↑ intracellular Ca²⁺ which damages or kills neurons

31
Q

Examples of neurodegenerative diseases

A

Parkinson’s, Alzheimer’s, MS

32
Q

Where do stem cells exist in fetal brain?

A

Venticular and subventricular zone

33
Q

Where do stem cells exist in adult brain?

A

1) Olfactory bulb<br></br>2) Dentate gyrus granule cells in the hippocampus

MedST IB: Neurobiology and Human Behaviour (NHB) (11 decks)

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