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Med School Yr 2 > 1 - Neuroembryology > Flashcards

1 - Neuroembryology Flashcards

1
Q

what environmental factors can cuases neurodevelopment defects?

A

alcohol
tobacco
nutrional deficiencies

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2
Q
A
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3
Q

Outline the basic developmental stages in the first 12 weeks of pregnancy, during the weeks:
1. week 0
2. week 2
3. week 3
4. week 3-8

A
  1. implantation
  2. blastulation
  3. gastrulation
  4. organogenesis
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4
Q

Outline the process of implantation in 6 steps:

A
  1. Blastocyte enlarges as it obtains nutrients from glycogen rich fluid secreted from endometrium.
  2. On contact with endometrium - trophoblast cells in blastocyte divide rapidly increasing thickness of throphoblast layer.
  3. Cytotrophoblasts (closest to interior) differentiate into syncytiotrophoblasts – break down stratum functionalis by secreting hyaluronidase
  4. Produce hCG – binds to CL + sustains it.
  5. Decidual change
  6. Blastocyst is burrowed into stratum functionalis + endometrium closes
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5
Q

outline the 4 major outcomes in blastulation:

A
  • Trophoblast differentiates into two layers – cytotrophoblasts and syncytiotrophoblasts
  • Embryoblast forms two layers – hypoblast + epiblast
  • Extraembryonic mesoderm – somatic layer + splanchnic layer
  • Two cavities form – amniotic cavity + yolk sac
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6
Q

in what weeks does embryogenesis occur?

A

0-8

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7
Q

in what week does gastrulation occur?

A

week 3

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8
Q

what occurs in week 3 of fetal development?

A

gastrulation

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9
Q

outline the 3 basic steps of gastrulation:

A
  1. Primitive streak formed on base of amniotic cavity
  2. Epiblast cells migrate towards the streak and slip beneath it – invagination
  3. Leads to formation of 3 germ layers
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10
Q

what are the 3 germ layers formed during gastrulation called?

A
  • ectoderm
  • mesoderm
  • endoderm
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11
Q

what does the ectoderm give rise to?

A

nervous system

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12
Q

during what weeks does organogenesis occur?

A

weeks 3-8

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13
Q

at what point in fetal development does the nervous system begin to form?

A

between 19-21 days AF

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14
Q

when does most nervous sytem development occur?

A

during embryogenesis

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15
Q

what are the 3 stages of nervous system development?

A
  1. induction of neural plate
  2. patterning of CNS
  3. neuronal differentiation/neurogenesis
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16
Q

the mesoderm develops into what?

A

somites –> skeletal and muscle tissue

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17
Q

the endoderm develops into what?

A

epithelium of organs

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18
Q

what process leads to the formation of the neural plate?

A

gastrulation

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19
Q

what forms directly beneath the primitive streak from mesoderm cells?

A

notochord

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20
Q

what is the notochord composed of?

A

mesoderm cells

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21
Q

what is the role of the notochord?

A

secretes growth factors which stimulates the differentiation of ectoderm into neuroectoderm

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22
Q

in what week of development does the notochord appear?

A

third week

23
Q

describe the folding of the neural plate

3 steps

A
  1. median hinge point forms - notochord signalling
  2. lateral hinge points form - signalling from nearby mesoderm
  3. meet in midline to form neural tube
24
Q

what structure forms as the neural folds fuse?

A

neural crest - then delaminates and migrates

25
Q

what does the neural crest give rise to?

A

a diverse cell lineage incl. melanocytes, craniofacial cartilage and bone

26
Q

when is neurulation achieved by?

A

end of the fourth week of development

27
Q

in 4 steps, outline the induction of the neural plate to form the dorsoventral axis

A
  1. induction
  2. elevation
  3. convergence
  4. closure
28
Q

in what region does neurulation first occur?

A

cervical region

29
Q

what happens after neurulation occurs in the cervical region?

A
  • neural tube zips up toward head and tail
  • leaves anterior and posterior neuropores
30
Q

when does the anterior neuropore close?

A

day 25

31
Q

when does the posterior neuropore close?

A

day 28

32
Q

what occurs if the anterior neuropore fails to close?

A

anencephaly - loss of telencephalon

usually results in death

33
Q

what happens if the posterior neuropore fails to close?

A

spina bifida

34
Q

what is the main goal of patterning of the nervous system?

A

helps cells acquire specific identities

35
Q

what are morphogens?

A

secreted proteins that act in a dose dependent manner

36
Q

what are the two main morphogens that act across the dorsoventral axis of the neural tube/

A

BMP - bone morphogenetic protein
SHH - sonic hedgehog

37
Q

w

what morphogen is secreted in the dorsal “roof plate” of the nervous system?

A

BMP

38
Q

what morphogen is secreted in the ventral “floor plate” of the nervous system/

A

SHH

39
Q

what determines the identities of neurons along the DV axis?

A

combination of SHH and BMP gradients

40
Q

a cell with motor neuron status has what relative levels of SHH and BMP?

A

high SHH
low BMP

41
Q

list these transcription factors according to location in the dorsoventral axis:
* Olig2
* pax7
* pax6
* Nkx6.1

(from most dorsal to most ventral)

A
  1. Pax7
  2. Pax6
  3. olig2
  4. Nkx6.1
42
Q

what is the antero-posterior axis also known as?

A

rostral-cordal axis

43
Q

how is the nervous system patterned along the AP axis?

A
  • posterior region secretes fibroblast growth factor
  • somites (found centrally) secrete reinoic acid
  • forms opposing gradients
  • cells closer to RA secretion acuire spinal cord identity
44
Q

what determines patterning in the anterior part of the CNS (the brain, not the spinal cord)?

A

combination of the morphogen signals from DV axis and diffusible molecules from AP axis

45
Q

holoproscencephaly

A

failure of the proscencephalon (embryonic forebrain) to divide into two hemispheres

46
Q

what causes holoprosencephaly?

A

mutation in SHH

47
Q
A
48
Q

morphogens are responsible for patterning the AP axis. what else is required for this?

A

homeotic genes

49
Q

what is neurogenesis?

A

process through which nurones are formed in the developing embryo

50
Q
A
51
Q

neural progenitor cells are polarised. at which surface do they proliferate - apical or basal?

A

apical (nucleus moves back and forward from apical to basal surfaces)

52
Q

in early development, how do progenitor cells divide?

A

symmetrically- equal inheritance of polarity complex proteins

53
Q

during later stages of development, how do progenitor cells divide?

A
  • asymmetically
  • one daughter cell becomes a neuron
  • other dauther cell becomes a progenitor cell and divides again
54
Q
A

Med School Yr 2 (96 decks)

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