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Developmental Neurobiology > Lecture 3- Induction of the Nervous System I > Flashcards

Lecture 3- Induction of the Nervous System I Flashcards

1
Q

What is the polarity in the 8-cell human embryo?

A
  • none apparent pre-implantation
  • after 3 divisions
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2
Q

What is the polarity in a 3 week old human embryo?

A

-post-implantation, axis apparent but shifted when compared to an adult

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3
Q

What are the axes like in an adult human brain?

A

-

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4
Q

What are the 7 stages of neural development (in order)?

A
  1. Neural induction
  2. Neurulation
  3. Morphogenesis and patterning of the neural tube
  4. Neurogenesis
  5. Neuronal migration
  6. Axon growth and pathfinding
  7. Synaptogenesis
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5
Q

What is neural induction (stage 1 of neural development)?

A

-assigning neural potential to a region of early embryo

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6
Q

What is neuralation (stage 2 of neural development)?

A

-forming the rudimentary nervous system

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7
Q

What is neurogenesis (stage 4 of neural development)?

A

-productions of neurons and glia from precursor cells

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8
Q

What is neuronal migration (stage 5 of neural development)?

A

-neurons move from sites of production to their position in the mature brain

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9
Q

What is axon growth and pathfinding (stage 6 of neural development)?

A

-axons grow and find appropriate target and dendritic arborization takes place

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10
Q

What is synaptogenesis (stage 7 of neural development)?

A

-making and refining connections

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11
Q

Why are amphibians good models to study early neural development?

A
  • have large eggs (1mm diameter)
  • develop externally of the mother so can work on them more easily
  • see-through embryo and egg
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12
Q

What is a blastula and when is the developing embryo called blastula?

A
  • a hollow sphere of cells, referred to as blastomeres, surrounding an inner fluid-filled cavity called the blastocoele formed during an early stage of embryonic development in animals
  • embryo development begins with a sperm fertilizing an egg to become a zygote which undergoes many cleavages to develop into a ball of cells called a morula. Only when the blastocoele is formed does the early embryo become a blastula.
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13
Q

What is a blastocoele?

A

the fluid-filled central region of a blastula and mammalian blastocyst (same as blastula but specific to mammals)

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14
Q

What is a gastrula?

A

-the stage in the embryo development in which the three germ layers are established after involution of blastula cells

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15
Q

What is involution?

A
  • process in the early development of an embryo at the beginning of gastrulation (so shoft from blastula to gastrula) where a sheet of cells moves into the interior of the embryo by rolling in under itself
  • creation of the germ layers
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16
Q

What does the nervous system arise from?

A
  • region of the dorsal ectoderm
  • called the neuroectoderm or neurogenic region
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17
Q

What is a blastopore?

A
  • an opening into the archenteron during the embryonic stages of an organism
  • will become the anus (or mouth, depends if protostome= mouth first or deuterostome= anus first, humans= anus first)
18
Q

What is the archenteron?

A

-the primitive gut, blastopore is its opening

19
Q

What does the ectoderm that won’t be part of the nervous system become?

A

-the epidermis of the skin

20
Q

What is the IMZ (Involuting Marginal Zone)/ DLB (dorsal lip of blastopore)?

A
  • region of cells immediately above the blastopore lip which narrows and lengthens internally during gastrulation
  • creates mesoderm
21
Q

What is a neurula?

A

-the stage of vertebrate development at the end of gastrulation when the neural tube is forming

22
Q

What is the notochord?

A
  • in vertebrate embryos it is a rod-like structure that runs from head to tail and lies centrally beneath the future central bervous system
  • it is derived from dorsal mesoderm
  • it plays an important role in patterning the overlying neural tube
23
Q

What happens to neuroectoderm at the beginning of neuralation?

A
  • it spreads anteriorly and becomes the neural plate
  • the anterior part will become the brain, posterior will become the spinal cord
24
Q

What does the notochord develop from?

A

-from a region of the mesoderm underlying the neural plate

25
Q

What is gastrulation like in a chick? (5)

A
  1. the posterior epiblast thickens
  2. cells move toward the primitive streak down through it and forward
  3. the primitive streak narrows and lengthens…
  4. …forming the primitive groove- the chick blastopore
  5. cells passing over Hensen’s node form head structures
26
Q

What is gastrulation?

A

-a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar (“three-layered”) structure known as the gastrula

27
Q

What is Hensen’s node?

A

-equivalent of dorsal lip of blastopore or the IMZ (but here in a chick embryo)

28
Q

What is inner cell mass in a human embryo?

A

-embryonic stem cells derive from there

29
Q

What is early human embryonic development like? (picture)

A

-

30
Q

What is the crucial interaction involved in induction of neural fate?

A

-interaction between the IMZ and the ectoderm

31
Q

What does transplanted IMZ induce?

A
  • a secondary nervous system
  • induces a neural fate in host cells that would normally form skin
32
Q

What is the secondary nervous system, brought about by IMZ transplantation, derived from?

A

-derived from host cells although graft produced notochord

33
Q

What are the two roles of IMZ?

A
  1. organizer of entire body axis
  2. induces the formation of a nervous system
    - called also Spemann’s organizer
34
Q

What happens when you take the neurogenic region out of the embryo in the pregastrular and gastrular stage?

A
  1. pregastrular (blastula): the tissue develops into epidermal tissue when isolated
  2. gastrular: the tissue develops into neurons
35
Q

How was the organizer molecule discovered?

A

-by in vitro assays

36
Q

What are the hemispheres called in a blastula?

A
  • upper: animal
  • lower: vegetal
  • middle: equatorial region that develops into the mesoderm
37
Q

What was observed when the dorsal ectoderm tissue was cultured by itself?

A
  • by itself it differentiates into epidermis
  • but when dorsal ectodermal cells are cultured by themselves at low density (without any possibility of communication) they follow a neural state
38
Q

What is the default model of dorsal ectodermal cells?

A
  • neural
  • signalling between closely-packed ectodermal cells overrides neural fate and induces epidermal fate
  • separating ectodermal cells reduces strength of signalling between them (dilutes signaling factor) and they develop into neurons
39
Q

What role does the organizer molecule play in neural induction?

A
  • it induces neural fate in dorsal ectoderm by repressing signalling between ectodermal cells
  • the molecule comes from the mesoderm
40
Q

What is the neural fate induced by?

A

-molecular signals from the organizer/ node

Developmental Neurobiology (32 decks)

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