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neuroscience > early development of the nervous system > Flashcards

early development of the nervous system Flashcards

1
Q

what are the 3 layers formed during gastrulation?

A

ectoderm, mesoderm, endoderm

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2
Q

when does gasturalation start and when does neurulation occur?

A

@7 days

neurulation occurs at the same time as gastrulation

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3
Q

what is the primitive streak?

A

it defines the midline ( starts in the posterior and proceeds anteriorly

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4
Q

what happens by the end of gastrulation?

A

the midline of of the embryo is defined by the formation of the notochord.

this is critical for the formation of all tissue including the CNS.

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5
Q

what is the first event in neurogensis?

A

the formation of neural ectoderm which is induced by the defined midline ( notochord formation)

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6
Q

what is the notochord formed of?

A

mesoderm and is a transient structure which is completely replaced by the neuroplate in humans

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7
Q

if ectoderm is exposed to bone morphogenic proteins (BMPs) then they become___________

A

epidermis

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8
Q

if ectoderm exposed to noggin/chordin (( and follistatin) all produced in the notochord) then it becomes____________

A

neuroectoderm

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9
Q

noggin and chordin inhibit_____________

A

bone morphogenic proteins (BMPs)

thus in the absence of BMPs ectodermal precursor cells will become neurons

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10
Q

bone morphogenic proteins (BMPs) come from ?

A

mesoderm

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11
Q

BM binds to ____________ and ___________ that is transported to the nucleus to mediate transcription.

A

receptor kinases and a SMAD complex

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12
Q

Besides inhibition of BMP, inhibition of what other signaling promotes stem cell commitment to neural cells?

A

inhibition of:

  1. Nodal signaling
  2. Wnt signaling
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13
Q

stimulation of ________,____________, and ___________ induce neural stem cell formation

A

retinoid acid (RA)
fibroblast growth factor (FGF)
insulin-like growth factor (IGF)

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14
Q

why is it that when separated ( a petri dish for e.g.) from the other layers ( mess and endo -derm) does ectoderm form neurons but when intact it forms epidermis?

A

because BMPs needed to form epidermis comes from mesoderm.

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15
Q

what does fibroblast growth factor (FGF) do?

A

it stimulates production of nogin which in turn inhibits BMP and leads to neural induction.

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16
Q

what cells make up the neural tube?

A

neural stem cells

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17
Q

after neural induction what happens to the neural plate?

A

the lateral margins of the neural plate fold inward to form the neural tube.

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18
Q

the floor plate and roof plate of the neural tube are key for_______

A

signaling

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19
Q

the central nervous system is a ( think shape)____________

A

a tube

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20
Q

_____________, particularly _____________ is important for the closure of the neural tube.

A

b-complex vitamins, especially folic acid

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21
Q

what is anencephaly?

A

lack of fore brain

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22
Q

what does the neural crest give rise to?

A

peripheral nervous system, cartilage, bone, connective tissue, pigment cells, and sympathy-adrenal cells

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23
Q

what are some neural tube closure defect?

A

spina bifida ( most common)- failure of posterior end of the neural tube to close

anacephaly and holoprosencephaly ( both typically deadly)

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24
Q

formation of the neural plate and neural groove are _________dependent

A

sonic hedgehog dependent

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25
Q

sonic hedgehog is expressed____________

A

is expressed only in the notochord and fore plate

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26
Q

the ventral signal ( motor) is?

A

sonic hedgehog (Shh)

27
Q

the dorsal signal ( sensory) is?

A

TGF betas ( mainly BMP)

28
Q

Sonic Hedgehog absence in the roof plate produces _______

A

dorsal-ventral polarity ) see pg 42

29
Q

describe Sonic hedgehog signaling (Shh)

A

Shh binds to patched protein which relieves Patched protein dependent inhibition of smoothened thus changes the identity of the cell (cell fate).

30
Q

what does smoothened do?

A

smoothened activates the Gii class zinc finger transcription factors

31
Q

what does Gli do?

A

Gli induces transcription and leads to a ventral (motor neuron) cell fates.

32
Q

what can absence of Shh result in?

A

holoprosencephaly - forebrain does not form and Dorsal ventral pattern is disrupted.

cancers like: medulloblastomas, and basal cell carcinoma

cyclopia- one eye ( seen in humans and in sheep ( sheep ate cyclopamine and Shh antagonist))

33
Q

what does Shh regulate?

A

polarity and proliferation

34
Q

in addition to BMPs and Shh pathways ______ and _________play a key role in dorsal ventral pattenrning

A

retionic acid ( RA) and fibroblastic growth factor (FGF)

35
Q

what are Hox genes?

A

transcription factors critical for body plan ( patterning): really only for the hindbrain, research is going on to figure out what goes on in the forebrain

36
Q

what is symmetric differentiation?

A

differentiation into 2 neurons or 2 neuronal stem cells

37
Q

what is asymmetric differentiation?

A

differentiation into a neuron and a different neuronal stem cell

38
Q

where do nerve stem cells proliferate and differentiate?

A

in the ventricular zone ( which surrounds the CSF-filled ventricles)

39
Q

inhibition of notch gives rise to?

A

neurons

40
Q

what cells have a lot of notch?

A

neurostem cells which inhibits pro neural genes and keeps it in a pleuripotent state and down regulates delta

41
Q

what do pro neural genes do?

A

they inhibit differentiation of glia

42
Q

why does the brain get bigger after birth?

A

brain gets bigger because of continuing connections made after birth and myelination

43
Q

what does anterior posterior patterning lead to?

A

spinal cord, rhombencephalon ( future pons and medulla), mesencephalon- future midbrain, prosencephalon ( future thalamus and retina, and future forebrain

44
Q

how do hox genes work?

A

by repressing and enhancing each other to create unique patterns of gene expression in each segment

45
Q

neural progenitors give rise to?

A

neurons and glia

46
Q

in early development how to neural stem cells divide?

A

symmetrically

47
Q

as development continues how doe neural stem cells divide ?

A

asymmetrically

48
Q

late in development how do neural stem cells divide?

A

symmetrically but giving rise toe 2 neural precursors thus neural stem cells disappear

49
Q

how do neural precursor cells divide?

A

symmetrically and asymmetrically

50
Q

neurogensis proceeds ____________

A

gliogenesis

51
Q

vitamin A excess or to little vitamin A, or drug abuse lead to?

A

birth (neural) defects

52
Q

cells made earlier are closer to the ________ and cells made later are closer to the ______

A

ventricular surface

pial surface

53
Q

where are projection neurons made?

A

the ventricular zone

54
Q

what is lissencephaly?

A

failure of gyri ( or fold ) formation

55
Q

where are interneurons made?

A

in the lateral or medial ganglionic eminence along the ventricular zone

56
Q

what path do interneurons take?

A

the tangential path for migration through the CSF. they migrate based on where the projection neurons went.

57
Q

when does neurogenesis in humans end?

A

by the end of the middle of the second trimester ( 19 weeks)

58
Q

when does gliogenesis end in humans?

A

sometime after birth ( to about 20 years old)

59
Q

when is primary neurulation complete?

A

within the first 3 weeks of pregnancy

60
Q

how does the cortex form?

A

in an inside out manner the first layer formed is closest to the ventricular zone

61
Q

what do radial gill cells do?

A

they rise to neurons and provide scaffolding on which they can migrate to their appropriate destination ( see pg 68)

62
Q

what does a mutation in the extracellular matrix protein reel in do?

A

results in a disruption of radial migration and causes earliest neurons to be on the outer surface rather than the inner surface near the ventricular zone.

63
Q

what are Mash1 and DLX1 and DLX2 involved in?

A

interneuron tangential migration

64
Q

describe how notch and Bhlh signaling resulate neural stem cell differentiation

A

see board (fill in later)

neuroscience (32 decks)

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