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2nd year see 1: Nueordevelopment > L3: Development of the spinal cord (finished) > Flashcards

L3: Development of the spinal cord (finished) Flashcards

1
Q

what are the segments of the spinal cord?

A 
cervical
thoraic 
lumbar 
sacral 
coccygeal
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2
Q

what does the cervical region support?

A

head and neck

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3
Q

what does each segment contain?

A

neurons

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4
Q

what do the neurons in each segment do ?

A

control or sense their related body segment

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5
Q

neurones are arranged in _____ regions depending on _______

A

specific

function

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6
Q

Different neuron clusters within a segment may control what?

A

different muscle groups

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7
Q

where does the notochord form from?

A

forms from the mesoderm cells soon after gastrulation is complete

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8
Q

Signals from the notochord cause uneven ______ and closing of the _____ _____

A

proliferation

neural plate

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9
Q

At early stages the neural tube is still in close proximity to what?

A

the mesoderm somites and notochord and also the epidermal cells of the ectoderm.

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10
Q

Cells of the neural tube form a __________ epithelium with the nuclei of dividing cells located at the _______ surface

A

pseudostratified

luminal

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11
Q

pseudostratified layer of cells include what?

A

neural stem cells or precursor cells

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12
Q

where is the luminal surface located ?

A

middle of the neural tube

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13
Q

exterior cells deliver _____ to the cord

A

signals

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14
Q

what happens to the cells receiving less signals?

A

they are are unspecified until they receive specifying signals as they migrate outwards

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15
Q

where do cells differentiate?

A

Cells differentiate as they migrate outwards, eventually the cells at the luminal border will also differentiate

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16
Q

what stem ependyma ?

A

the thin membrane of glial cells lining the ventricles of the brain and the central canal of the spinal cord.

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17
Q

what forms the ependyma ?

A

ependymal cells

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18
Q

what 3 layers become visible?

A

ventricular layer, mantle layer, marginal layer

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19
Q

what is the ventricular layer?

A

undifferentiated, proliferating cells

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20
Q

what is the Mantle layer ?

A

differentiating neurons (form grey matter)

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21
Q

what is the marginal layer?

A

contains nerve fibres (form white matter)

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22
Q

what does the alar plate form?

A

the sensory area (dorsal horn)

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23
Q

what does the basal plate form?

A

the motor area (ventral horn)

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24
Q

what happens to Neuroblasts ?

A

start large but decrease in size and become multipolar

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25
Q

Neural tube develops in different ways along what?

A

along the rostrocaudal axis such that cells in different regions of the neural tube will start to acquire regional identities.

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26
Q

formation of the different early brain regions and also the spinal cord are mediated by what?

A

patterned signalling which drive cells to different fates

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27
Q

signalling which drive cells to different fates, comes form where?

A

the surrounding mesoderm and by the endoderm

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28
Q

what happens when cells respond to signal that choose their fate?

A

cells change their transcriptional profile so that it is different in different areas of the neural tube.

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29
Q

what happens when cells change their transcriptional profile?

A

restrict/define what these cells will become and what they can respond to.

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30
Q

what protein is important in early regionalisation ?

A

Wnt proteins

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31
Q

what happens with Wnt proteins across the rostral caudal axis?

A

There is a gradient of Wnt activity, probably mediated by Wnt inhibitors along the rostral caudal axis.

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32
Q

does the rostral region have high or low Wnt signalling ?

A

low

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33
Q

what region has high levels on ant signalling ?

A

caudal region

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34
Q

what does the caudal region become?

A

hindbrain and spinal cord

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35
Q

what does the rostral region become?

A

fore and mid brain

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36
Q

dorsoventral patterning is first mediated by what?

A

signals from the surrounding tissue

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37
Q

mesoderm and ectoderm are close to what?

A

close to the dorsal or ventral parts of the neural tube

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38
Q

what establishes ventral signals?

A

Ventral signals are established intially by the notochord

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39
Q

whats the notochord?

A

a long region of mesoderm running parallel to the neural tube

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40
Q

the disoventral patterning signals are eventually transferred to where via what?

A

to the neural tube through the floor plate

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41
Q

Dorsal signals are initiated by ? and are passed on to where?

A

Dorsal signals are initiated by epidermal/ectoderm cells and are passed on to the roof plate within the neural tubes itself.

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42
Q

dorsal signalling will generate what?

A

dorsal neurons

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43
Q

ventral signalling will generate what?

A

ventral neurons

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44
Q

How are Ventral horn neurons specified?

A

by Shh signalling

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45
Q

where is Shh released from?

A

released Initially from the notochord

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46
Q

what does Shh do?

A

instigates ventral neural tissue characteristics

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47
Q

where does the signalling go after rSh is released from the notocho?

A

signalling is later passed to the floor plate

48
Q

Shh is highly concentrated where?

A

at the most ventral part of the developing SC

49
Q

where does Shh diffuse towards?

A

towards to the more dorsal part

50
Q

Sonic hedgehog is a what?

A

a morphogen

51
Q

what does being a morphogen mean?

A

This means that it can instigate different cell responses along a gradient of concentration.

52
Q

At different concentration levels of Shh cells responds…

A

differently, there a number of types of cell response which are distinct from eachother

53
Q

How does Shh cause different types of cell responses depending on concentration?

A

by switching on/off expression of different transcription factors when the cells are exposed to higher and higher concentrations.

54
Q

where is the highest concentration of Shh?

A

most ventral part of the cord the floor plate

55
Q

how many and which transcription factors are expressed at the floor plate?

A

Two, Nkx2.2 and Nkx6.1. other 5 repressed

56
Q

shh has a _____ effect at the furthest point away which means ___ TF are on

A

minimal

5

57
Q

what do these tf control?

A

genes which will set the cell on a path towards a certain specification of neurons.

58
Q

Sonic hedgehog signalling drives what?

A

ventral neuron patterning

59
Q

Neurons experience different levels of ___ which leads to ____ transcription factor expression

A

Shh

different

60
Q

what does Transcription factor pattern dictate?

A

neurone identity

61
Q

each part of the ventral horn has a specific transcription factor profile, what does this establish?

A

establishes the specific cell types found at these locations.

62
Q

there is a specific profile of transcription factors for every type of cell example…

A

cells can be pushed towards motor neurones

63
Q

early on motor neurone cells are referred to as what?

A

(progenitor) pMN which then lead to mature motor neurons

64
Q

transcription factors ______ their opposite transcription factor.

A

repress

65
Q

ventral horn, contains what and receives input form what?

A

lower motorneurones

higher motorneurones

66
Q

input from MN are sent t the VH how?

A

direct from cortex OR others are polysynaptic via the red nucleus and from vestibular nuclei.

67
Q

striated muscle is what type of muscle?

A

voluntary

68
Q

what do ventral neurones produce ?

A

axons

69
Q

what do axons produced by ventral neurones do?

A
  • grow out along ventral roots to innervate striated (voluntary) muscle.
  • innervate autonomic ganglia.
70
Q

when are all major ventral columns visible?

A

14 weeks

71
Q

what type of neurones are dorsal neurones?

A

Dorsal neurons are the sensory neurons and are often somatotopically arranged

72
Q

in the dorsal region what drives regionalisation?

A

BMP signalling

73
Q

length of exposure to BMP is a ?

A

regulating factor

74
Q

dorsal horn neurones are derived form where?

A

from the alar plate

75
Q

many dorsal horn neurones become what?

A

many become interneurones receiving input from sensory neurones

76
Q

At the end of the 4th week, axons grow in from ____ ____ ______ to synapse with them

A

dorsal root ganglion

77
Q

Dorsal column neurones produce ____ that ascend the _____ ___ by the end of the ____ ____.

A

axons
spinal cord
3rd month

78
Q

during developement of the dorsal horn what happens by the fifth month?

A

spino-thalamic and spino-cerebellar fibres have ascended to the brain, carrying sensory information from the spinal cord at all levels.

79
Q

Antiparallel signalling gradient precisely dictates what?

A

cell specification

80
Q

how are spinal cord motor neurones arranged?

A

in pools

81
Q

each section of motor neurones have what?

A

have specific muscular targets

82
Q

LMC motor neurons innervate the?

A

limbs

83
Q

what are some pools of motor neurones?

A

PMC = Phrenic motor column; LMC = Lateral motor column; PGC = Preganglionic column; MMC = Medial motor column

84
Q

How are the neurons specified to these pools?

A

using Hox genes

85
Q

what are the steps to how neurones are specified to these pools?

A
  • During development neural tubes is exposed to graded levels of morphogens
  • Cells exposed to different levels of retinoic acid and FGF8 will express different Hox genes
  • expression of Hox gene determines what motor neurone class is generated.
86
Q

These transcription factors switch on specific genes - some of which specify what?

A

axonal guidance

87
Q

Hox expression profile specifies what?

A

which muscle group motor neurons will target

88
Q

Hox profile also controls what?

A

axonal guidance receptor expression. E.g. Ephrin receptors

89
Q

Specific ephrin receptors bind specific ephrins which act as ___ ___

A

repulsive cues

90
Q

How are axons guided in the lumbar column?

A

In the lumbar column, axons are guided to ventral or dorsal muscles depending on Ephrin A or B receptor expression

91
Q

Higher EphA receptor =

A

repulsion from ventral area where there is a high level of EphA

92
Q

Following fusion of the neural folds, what happens to neural crest cells?

A

neural crest cells leave the dorsal aspect of the developing spinal cord.

93
Q

Many of the neural stem cells leaving the dorsal aspect of the developing spinal cord move to form ?

A

the sensory neurons of the spinal (dorsal root) ganglia.

94
Q

How do Cells in the dorsal root ganglia extend sensory fibres ?

A

extend sensory fibres both centrally and peripherally

95
Q

motor axons grow out from the neurons in the?

A

basal plate.

96
Q

where do Oligodendrocytes (myelinate nerve fibres) appear from ?

A

from ventral and dorsal regions of the spinal cord

97
Q

WHAT ARE Ventrally derived oligos directed by?

A

Shh signalling

98
Q

______ appear latest in development from ventricular regions of the spinal cord

A

Astrocytes

99
Q

where do astrocytes populate?

A

Populate all areas of spinal cord (grey and white matter)

100
Q

Microglia invade the CNS apparently with ______

A

vascularisation

101
Q

true or false, All spinal cord nerve fibres are initially unmyelinated.?

A

true

102
Q

what are Dorsal and ventral nerve roots myelinated by?

A

Schwann cells (arising from the neural crest) at 5 months.

103
Q

where do schwann cells come from?

A

from the neural crest

104
Q

Axons within the spinal cord are myelinated by ?

A

oligodendrocytes.

105
Q

Most descending fibres are myelinated at ?

A

nine months.

106
Q

some descending fibres are not myelinated until?

A

one year after birth.

107
Q

Many ascending neurons remain unmyelinated.

, true or false?

A

true

108
Q

Most spinal cord defects are a result form what?

A

abnormal closure of the neural folds in the 3rd and 4th week

109
Q

whats the most common neural tube defect?

A

spina bifida

110
Q

what enrol tube defect is Occulta?

A

vertebrate provides incomplete coverage

111
Q

what is Meningocele?

A

– meninges herneate

112
Q

what is Myelomeningocele ?

A
  • Spinal cord herneates
113
Q

Dorsal horn is specified by ?

A

BMP Signalling

114
Q

Glial cells develop after what?

A

neurogenesis

115
Q

Dorsal root ganglia are derived from where?

A

the neural crest

2nd year see 1: Nueordevelopment (4 decks)

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