Lecture 23 Flashcards

1
Q

gastrulation is __

A

the local invagination of a subset of cells in the early embryo

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2
Q

gastrulation creates _ germ layers: ___

A

3; ectoderm, mesoderm, endoderm

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3
Q

ectoderm =

A

nervous system, epidermis

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4
Q

mesoderm =

A

notochord, bone, muscle, connective tissue, gonad

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5
Q

endoderm =

A

GI tract, respiratory tract, endocrine system, auditory system, urinary system

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6
Q

the initiation of neural development is critically dependent on what two processes?

A

gastrulation and neurulation

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7
Q

when the process of gastrulation is complete, the embryo will consist of __

A

3 germ layers (ectoderm, mesoderm, endoderm)

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8
Q

an important event in the process of __ is the formation of the notochord

A

gastrulation

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9
Q

the formation of the notochord ___ is very important

A

at the midline of the gastrulating embryo

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10
Q

the notochord is a __ of __ cells, which condense at the __ as ___

A

cylinder; mesodermal; midline; the mesoderm invaginates

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11
Q

the notochord extends from the __ to the __

A

anterior to posterior

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12
Q

during late gastrulation, mesodermal cells in the region of the primitive streak form the __

A

notochord

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13
Q

the notochord is a critical feature - it directs the __ (secretes __)

A

formation of the nervous system; secretes inductive factors

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14
Q

the layer of ectoderm that lies right above the notochord is called the __ which is tiny but gives rise to __

A

neuroectoderm; the entire nervous system

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15
Q

the notochord defines the __ of the embryo; lays out the __ for the entire body

A

midline of the embryo; symmetry

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16
Q

primitive pit is __; which leads to the __, leads to the __

A

the very first dent; leads to the primitive streak, which leads to the notochord

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17
Q

the notochord induces the neuroectoderm to ___

A

differentiate into precursor cells that thicken and become the neural plate

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18
Q

the neural plate is just the __ in another phase/state

A

neuroectoderm

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19
Q

cells from the __ and the __ send chemical/molecular signals to the neuroectoderm, which causes a subset of cells to __…..this process intiates __

A

notochord and primitive streak; differentiate into neural plate precursor cells; neurulation

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20
Q

the thickening is called the __

A

neural plate

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21
Q

the lateral margins of the neural plate begin to __, which transforms the plate into a __

A

fold upward; tube

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22
Q

the cells within the neural tube give rise to __

A

the brain and spinal cord

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23
Q

those neuroectoderm precursor cells are the __. they are __ and have the capacity to __

A

progenitors of the neural tube; stem cells; give rise to any cell class found in the mature nervous system

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24
Q

neural crest cells are at the border of the __ and the __

A

neural plate and the non-neural ectoderm

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25
Q

neural crest cells are a __ group of cells and are unique to __

A

temporary; vertebrates

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26
Q

3 examples of what neural crest cells give rise to

A

cartilage, bone, smooth muscles

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27
Q

what are the “neural stem cells”?

A

the neuroectodermal precursor cells

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28
Q

how are neural stem cells different than embryonic stem cells?

A

they cannot give rise to ANYTHING, it has to be some neural tissue

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29
Q

neural stem cells divide to produce __

A

more precursor cells

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30
Q

neural stem cells give rise to __

A

neurons, astrocytes, oligodendrocytes, glia, etc.

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31
Q

what do neural stem cells depend on to determine what they become?

A

the local environment (molecular cues)

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32
Q

the neural tube also contains specialized epithelial-like cells called the __

A

floorplate

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33
Q

the floorplate secretes molecular signals that __

A

specify position and fate of neural progenitors

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34
Q

are all cells in the neural tube self-renewing?

A

no

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35
Q

neural tube also gives rise to a subset of progenitor cells called the __

A

neural crest

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36
Q

floorplate gives rise to __

A

hindbrain and spinal cord

37
Q

the neural crest differentiates into __

A

neurons and glia of the sensory and visceral motor ganglia, neurosecretory cells of the adrenal gland, and neurons of the enteric nervous system

38
Q

differentiation is dependent on __

A

the type of environment they end up in

39
Q

neural crest cells migrate and move along __

A

four distinct pathways

40
Q

4 pathways of neural crest cells

A

sensory, autonomic ganglia, adrenal neurosecretory cells, and melanocytes/non-neuronal cells

41
Q

cell signaling during migration influences __

A

progenitor identity and terminal differentiation

42
Q

soon after the neural tube forms, the ___

A

fore-runners of the major brain regions start to become more apparent

43
Q

soon after the neural tube forms, __ begins to shape the neural tube into different regions

A

morphogenesis

44
Q

primitive brain regions (4)

A

prosencephalon, mesencephalon, rhombencephalon, and spinal cord

45
Q

the first bend (towards the head) is called the __, which gives rise to the ___, which gives rise to the __

A

cephalic fixture; prosencephalon; forebrain

46
Q

the second bend (towards the tail) is called the __

A

cervical flexure

47
Q

the mesencephalon gives rise to the __

A

midbrain

48
Q

the rhombencephalon gives rise to the __

A

hindbrain

49
Q

neural tube forms a precursor to the __

A

spinal cord

50
Q

lateral aspects of the prosencephalon form the __, which gives rise to __ (4)

A

telencephalon; cerebral cortices, hippocampus, basal ganglia, and forebrain nuclei

51
Q

caudal aspects of the prosencephalon form the __, which gives rise to __ (3)

A

diencephalon; thalamus, hypothalamus, and optic vesicles/cups (eventually forming the retina)

52
Q

dorsal portion of the mesencephalon forms the __

A

superior and inferior colliculi

53
Q

ventral portion of the mesencephalon gives rise to the __

A

tegmentum

54
Q

rostral portion of the rhombencephalon forms the __ which gives rise to the __ (2)

A

metencephalon; cerebellum and pons

55
Q

caudal portion of the rhombencephalon forms the __ which becomes the __

A

myelincephalon; medulla

56
Q

how can this simple tube beget such a variety of brain structures?

A

genes

57
Q

the neural tube is organized into repeating units called __

A

neuromeres

58
Q

the segmentation establishes __

A

regional identity

59
Q

4 examples of homeobox genes

A

bcd, kr, h, wg (wingless)

60
Q

expression patterns of genes (___) guides the differentiation of the embryo into __ that gives rise to different regions of the body

A

homeobox genes; distinct segments

61
Q

homeobox genes are __ that direct the expression of other genes that mediate __

A

transcription factors; morphogenesis

62
Q

vertebrates also have __ which are expressed only in the __ (2)

A

hox genes; posterior hindbrain and spinal cord

63
Q

hox gene expression coincides with the __

A

formation of morphological features

64
Q

neural stem cells are __ cells that can give rise to __

A

multipotent; many different neuronal cell types

65
Q

neural stem cells must acquire __

A

instructions to terminally differentiate into the appropriate cell type

66
Q

when you transfer neuronal stem cells to a new region they can __ (2)

A

acquire the identity of that new region; retain an identity that reflects their origin

67
Q

when you remove neural stem cells, (3)

A

compensated by local proliferation; causes little change; disrupts development

68
Q

it is the __ that is essential for regional identity

A

interactions between cells

69
Q

neural induction =

A

just the instructions that tell a neural stem cell what to become

70
Q

genes are expressed in different areas of the neural tube

A

.

71
Q

local signaling molecules =

A

molecules that play a role in morphogenesis and/or neuronal differentiation

72
Q

sonic hedgehog is expressed and secreted by the __ (2)

A

notochord and floorplate

73
Q

sonic hedgehog is important for (2)

A

closing the neural tube; establishing the identity of neurons in the ventral portion of the spinal cord and hindbrain

74
Q

mutations of sonic hedgehog result in __

A

failed division

75
Q

when sonic hedgehog is present it binds to __ and ___, this causes disassembly of __ which goes on to affect genes

A

patch; __ ; protein GRI1

76
Q

BMP =

A

bone morphogenetic proteins

77
Q

the BMPs expressed in the __ promote __, and also turn ___ into __

A

mesoderm; osteogenesis; ectodermal cells; skin

78
Q

Noggin and chordin sequester BMP, preventing the __ cells from becoming __ and they instead form __

A

neuroendodermal cells; epidermis; neuronal tissues

79
Q

noggin and chordin are __ that modulate signaling via __

A

endogenous antagonists; TGF-beta family

80
Q

morphogenic factors exist in __

A

gradients

81
Q

the identity of motor and interneurons in the ventral vs dorsal spinal cord reflects the __

A

graded local signals of Shh, noggin, and other morphogens

82
Q

neurogenesis begins after __ is complete

A

initial patterning of the neural tube

83
Q

precursor cells have the __ that assign basic identities

A

signature gene expressions

84
Q

precursors are at the __ and differentiate there

A

ventricular zone

85
Q

precursors form __ or __

A

new neuronal stem cells or postmitotic neuroblasts

86
Q

precursor cells in the neural epithelium are attached at the __ and the _

A

ventricular surface and the __ surface

87
Q

during neurogenesis, the __ move, when the cell is closest to the __ surface of the neural tube it will undergo __

A

nucleus of the cells; outer (plial); DNA synthesis

88
Q

neuronal production and migration: symmetrical division yields __

A

2 identical progenitor cells

89
Q

neuronal production and migration: asymmetrical division yields __

A

1 progenitor cell and 1 neuroblast