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332: Neurobiology > 8. Development of the Nervous System > Flashcards

8. Development of the Nervous System Flashcards

1
Q

what is the first stage of embroygenesis

A

cleavage

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2
Q

describe the first two cleavages

A

perpendicular equal and holoblastic

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3
Q

why is cleavage 3 different from cleavage 1 and 2

A

it is no unequal and holoblastic

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4
Q

cleavage continues until how many cells are made

A

32

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5
Q

during cleavage what is the early embryo contained in

A

the zona pellucida

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6
Q

once it reaches 32 cells what is the embryo now termed

A

a morula

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7
Q

what occurs during the compaction stage

A

cells get closer together and the cells on the outside differentiate into trophoblast cells.

the inner cells are called embryoblasts

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8
Q

what occurs on day 5

A

embryoblast cells clump together at one end, the remainder of the space inside the layer of trophoblast cells becomes the blastocoel

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9
Q

what is a blastocoel

A

a fluid filled cavity

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10
Q

what happens to the zona pellucida on day 5

what does this facilitate

A

it decomposes and is replaced by the underlying layer of trophoblastic cells

this facilitates implantation into the endometrium

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11
Q

what then occurs to the inner cell mass

A

it flattens out, the two cells become epiblasts and the layer below become hypoblasts

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12
Q

what is the term given for the inner cell mass once it has flattened out

A

the bilaminar disk

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13
Q

once the bilaminar disk is formed, what happens next

A

the primitive streak forms at the midline of epiblast cells, from this they ingress into the blastocoel

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14
Q

what dictates epiblast fate

A

the order of which they enter the blastocoel

the first cells become endoderm
the middle cells become mesoderm
the last cells become ectoderm

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15
Q

name 2 things the endoderm goes on to form

A

liver
lungs

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16
Q

name 2 things the mesoderm goes on to form

A

muscle
blood

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17
Q

name 2 things the ectoderm goes on to form

A

all parts of the nervous system
ear
lens of eye…

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18
Q

what directs the migration of epiblast cells into the blastocoel

A

the organiser

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19
Q

what determines the dorso-ventral axis

A

the point of sperm entry = ventral side
from this microtubules contract and the cytoplasm rotates facilitating the formation of a signalling centre on the dorsal side

20
Q

what is the name of signalling centre generated in response to sperm entry

A

the nieuwkoop centre

21
Q

describe the process of mesoderm specification along the axis

A
  1. BMP4 is expressed in the marginal zone and induces ventral mesoderm
  2. VegT and Vg1 induce nodal-related in the vegetal hemisphere
  3. beta catenin boosts nodal related in the nieuwkoop centre which induces dorsal mesoderm and the organiser
  4. the organiser produces chordin which acts as a dorsalising signal
  5. colloid cleaves chordin in the vegetal hemisphere allowing BMP4 to act.
22
Q

what does the dorsal most aspect of mesoderm develop into

A

the notochord

23
Q

what does the ventral most aspect of mesoderm develop into

A

blood

24
Q

name the organiser in chicks

A

hensens node

25
Q

name the organiser in amphibians

A

spemann’s organiser

26
Q

name the organiser in mammals

A

primitive knot (or node)

27
Q

describe Spemann and Mangold’s experiment

A

they confirmed the role of the organiser by transplanting tissue from a pigmented embryo into a non-pigmented embryo

this could induce the formation of two new embryos by implanting the specific tissue that included the organiser

28
Q

what happens if you cut a blastula in two

A

the ventral side will not develop into muscle - only ventral mesoderm fates such as blood develop

the organiser must be present in the dorsal marginal zone to produce muscle

29
Q

what happens if you induce beta-catenin mRNA into the ventral side of the vegetal region

A

a second nieuwkoop centre will develop and duplicated axis will develop

30
Q

what signalling molecule is essential for specifying the nieuwkoop centre

A

Wnt

31
Q

what does the notochord form from after gastrulation

A

mesoderm cells

32
Q

what do signals from the notochord do?

A

drive inward folding of ectoderm at the neural plate

33
Q

what happens after the neural plate is formed

A

the ends fuse and disconnect to form an autonomous neural tube

34
Q

once the neural tube is formed, which bit does the brain and spinal cord develop from

A

the brain forms from the anterior end
the rest of the tube forms the spinal cord

35
Q

what tissue is the neural tube derived from

A

ectoderm

36
Q

what molecule inhibits neurulation

A

BMP4

37
Q

what happens to ectodermal cultures with BMP4

A

they differentiate into epidermis rather than neural cells

38
Q

name 3 molecules that inhibit BMP4

A

chordin
noggin
follistatin

39
Q

what is the evidence that BMP4 is an inhibitor of neurulation

A

KO mice for chordin and noggin = BMPs are not inhibited so epidermal fate is not inhibited and neural fate is not induced

produces mice without a forebrain, nose or facial structure

40
Q

do it again! describe the process of neurulation! hahah

A
  1. neuroectodermal cells dive down and differentiate into the neural plate
  2. on either side of the neural plate is a band of cells called the neural crest
  3. neural plate invaginate and the neural crest tissue sitting at the top forms the neural groove
  4. the neural groove pinches off forming an autonomous neural tube
41
Q

what do neural crest cells eventually produce

A

peripheral nervous system neurons

42
Q

what happens to the notochord after neurulation

A

it is only retained in some primitive chordates (e.g. hagfish)
in most higher order vertebrates it is replaced by the vertebral column

43
Q

what does fusion of the neural plate require

A

cell adhesion molecules: N-cadherin and N-CAM

44
Q

what process stops the binding of neural tissue to epidermis, and why

A

homophillic adhesion
they can now recognise each other as being the same

45
Q

neural crest cells show some plasticity, depending on their positional cues what do they produce?

A

either sympathetic or parasympathetic neurons depending on their anterior-posterior position.

332: Neurobiology (15 decks)

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