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21 fall: Dev Bio > test 2 lecture 18 -19 nervous system > Flashcards

test 2 lecture 18 -19 nervous system Flashcards

1
Q

The trilaminar embryo (aka trilaminar blastocyte) has three distinct layers

A
  • ectoderm
  • mesoderm
  • endoderm
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2
Q

The central and peripheral nervous systems are entirely derived from the ___ layer.

A

ectoderm

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3
Q

The development of the central and peripheral nervous systems is initiated by the induction of the ___ (occurs during gastrulation).

A

neural plate

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4
Q

___ is the the process by which neural plate is generated from ectoderm

A

neural induction

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5
Q

__ directs neural induction

A

notochord (part of mesoderm)

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6
Q

ectoderm stays epidermal ectoderm by binding with ___

A

BMP4

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7
Q

ectoderm turns into neural crest by

A

Chordin, Noggin and Follistatin are secreted by the dorsal
mesoderm/notochord

They bind BMP4 molecules inhibiting BMP4 interaction

act as BMP antagonists

antagonists to the protein and NOT the receptor

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8
Q

___ of BMP4 signaling in the ectoderm is required to convert the ectoderm into neural tissue (mediated by the dorsal mesoderm)

A

Inhibition

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9
Q

Noggin, Chordin and Follistatin act as ___

A

BMP antagonists

bind to BMP protein and prevent BMP from binding to its receptors

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10
Q

___ are secreted by the dorsal
mesoderm/notochord to stop BMP

A

Chordin, Noggin and Follistatin

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11
Q

___ is the default state of the ectoderm

(in the absence of BMP4 signaling)

A

Neural fate

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12
Q

transformation of the neural plate into the neural tube

A

Neurulation

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13
Q

The nervous tissue induced by BMP4 inhibition is anterior in character (___).

A

forebrain

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14
Q

neural induction is ___ neurulation

A

NOT

Neurulation = transformation of the neural plate into the neural tube

Neural Induction= The process by which the dorsal mesoderm induces the overlaying ectoderm to form neural tissue

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15
Q

The central nervous system is regionalized along the ___ axis.

A

anterior-posterior (AP)

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16
Q

what are the two models of induction and AP patterning of the neural plate

which one is correct?

A

different inducers at different spots

or

gradient of inducer

gradient is correct

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17
Q

Induction and AP patterning of the neural plate is a two-step process

A

Activation: Induction of anterior neural tissue mediated by inhibition of BMP4 signaling in the ectoderm by Noggin, Chordin, and Follistatin (made by notochord)

Transformation: A distinct set of signal(s) posteriorize the neural tissue. (FGF, retinoic acid, Wnt-3a_

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18
Q

What are the three posterior neural inducers

A

fibroblast growth factor (FGF) family,

Retinoic acid

Wnt-3a

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19
Q

neurulation

A

neural plate transforming into neural tube

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20
Q

two neural tube defects

A

errors when neural plate fails to close properly into neural tube

anencephaly- absence of major portion of brain/ skull

spina bifida- spine/spinal cord defect

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21
Q

The prospective brain is initially subdivided into three primary vesicles:

A

Forebrain (prosencephalon)

Midbrain (mesencephalon)

Hindbrain (rhombencephalon)

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22
Q

• Forebrain (prosencephalon) becomes

A
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23
Q

Midbrain (mesencephalon) becomes

A
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24
Q

hindbrain becomes ___

A
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25
Q

___ is the boundary between the midbrain and the hindbrain):

A

Isthmus

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26
Q

Isthmus

A

•the boundary between the midbrain and the hindbrain)

a critical region for the formation and the patterning of the midbrain.

•express signaling molecules (Wnt-1 and FGF8); acts as an organizing center.

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27
Q

if Wnt 1 is inhibited what will happen to midbrain?

if FGF8 is placed somewhere else what will happen?

A

will not develop

2nd midbrain will develop but in wrong direction

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28
Q

•The hindbrain is divided into periodic swellings known as ___

A

rhombomeres.

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29
Q

•The ___ represent separate “territories”, such that cells from one rhombomere cannot mix with cells from adjacent rhombomeres.

A

rhombomeres

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30
Q

In the hindbrain, ___ encode positional values along the anterior-posterior axis of the nervous system.

A

Hox genes

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31
Q

The identity of each ___is defined by the expression pattern (specific combination) of Hox genes.

A

rhombomere

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32
Q

It is unclear how Hox genes become activated at appropriate levels, although ___, ___, and ___ are likely regulators.

A

Retinoic Acid (RA)

Egr2

Mafb

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33
Q

how does retinoic acid effect hindbrain

A

more RA in posterior, effects which hox gene is expressed and which rhombomere is made.

if experiment is done and more RA is added to anterior of hindbrain then rhombomere 4 will form instead of rhombomere 1,2,3

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34
Q

zones of neural tube

A

marginal zone: neuroblasts, glioblasts

Ventricular zone: neural stem cells

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35
Q

Neuroepithelial cells are the precursor cells for ALL of the cells in the CNS (with one exception). what is the exception?

A

microglial cells

immune cells of the CNS

these come from mesenchymal cells

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36
Q

neuroepithelium can turn into what two major types

A

glial lineage progenitor cells

neuronal lineage progenitor cells

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37
Q

glial lineage progenitor cells can turn into

A

ependymal cells- lining of ventricles

type 1 astrocyte

Type 2 astrocyte

oligodenrocytes

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38
Q

Astrocytes

A

come from gilial lineage progenitor cells

Supporting cells: give physical and metabolic support, can regulate neuronal activity

39
Q

Oligodendrocytes

A

schwann cells

Myelinating cells: wrap axons with myelin, increasing speed of electrical transmission

40
Q

neuronal lineage progenitor cells lead to

A

mature neuron

1,000-10,000 types; electrical activity executes all the functions of the nervous system

41
Q

what can help orient ventral vs dorsal neural tube

A

group of non neural cells

roof plate

floor plate

42
Q

notochord will cause what to form in the neural tube?

A

floor plate

motor neurons

43
Q

The Notochord is the source of two inductive signals.

A

local signal that induces floor plate differentiation at the midline

long-range signal that induce motor neurons on each side

44
Q

The ___, once induced, acquires the ability to generate both short- and long-range signals.

A

floor plate

45
Q

Notochord secretes ___ to induce the formation of floor plate in the neural tube

A

sonic hedgehog Shh

46
Q

After formation of the Floor plate of the neural tube, the floor plate will secrete ___ making a gradient

A

Shh (sonic hedgehog)

47
Q

___ acts as a morphogen to generate neuronal diversity

A

Shh

48
Q

Graded amounts of Shh generate distinct populations of motor neurons and interneurons in the ___ portion of the spinal cord.

A

ventral

49
Q

dorsal differentiation of neural tube is by

A

Transforming growth factor (TGF-b) family

Bone morphogenetic proteins (BMPs)

Overlapping expression in the dorsal spinal cord

Neuronal diversity in the dorsal spinal cord is established as a result of a diversity in signal identity rather than signal intensity.

50
Q

Neuronal diversity in the dorsal spinal cord is established as a result of a ___ identity rather than signal intensity.

A

diversity in signal

loss of GDF7, a BMP related factor led to the selective loss of a single class of dorsal interneurons

51
Q

diversity and pattern in the neural tube

A

dorsal by different signals

ventral by gradient of Shh

52
Q

During neurulation, the neural crest is at the most ___ region of the neural tube

A

dorsal

53
Q

•To migrate, neural crest cells will undergo ___

A

epithelial-to-mesenchymal transition (EMT)

a process by which epithelial cells lose their cell polarity and cell-cell adhesion, and gain ability to migrate (and invasive properties).

54
Q

what are some things neural crest cells can turn into

A
55
Q

Upon neural tube closure, neural crest cells delaminate in a ___and migrate along specific routes.

A

rostro-caudal wave

56
Q

cranial neural crest cells turn into

A

derived from the hindbrain (rhombomeres 4,5,6)

migrate dorsolaterally

cells enter the pharyngeal pouches (2 and 3) and arches where they contribute to the thymus, bones of the middle ear and jaw, and the odontoblasts of the tooth primordia.

cartilage, bone, cranial ganglia and connective tissue of the face

57
Q

cardiac neural crest cells turn into

A

septum of the outflow tract of the heart (separates the truncus arteriosus into the pulmonary artery and aorta) and wall of large arteries

58
Q

neural crest induction

A

notochord releases anti BMP (noggin, chordin, follistatin) neural crest has happy medium of anti BMP

paraxial mesoderm release Wnt and FGF

non neural ectoderm release Wnt

Neural crest release Notch/Delta which inhibit BMP

59
Q

The __cells are a stem cell-like population. Some of these cells are multipotent which means __

A

neural crest

are able to generate numerous cell types (bone, cartilage, smooth muscle, neurons, pigment cells)

60
Q

neural crest diversification is dependent on local factors, an example is glial growth factor stimulates differentiation into ___, while endothelin-3 stimulates differentiation into ___

A

autonomic neurons

melanocytes and enteric neurons formation.

61
Q

All sensory cells of the peripheral nervous system (PNS) develop from various sources, but primarily from ___ and from thickenings of the ectoderm in the head region known as ___

A

neural crest cells

ectodermal placodes.

62
Q

The cell bodies of these sensory cells are located ___ the central nervous system.

A

outside

63
Q

The __consists of cranial, spinal and visceral nerves and ganglia.

A

PNS

64
Q

The spinal ganglia (dorsal root ganglia) are exclusively derived from ___ that migrate and accumulate on each side of the spinal cord to form the sensory spinal ganglia.

A

neural crest cells

65
Q

Spinal ganglia cell bodies project branches towards the ___part of the spinal cord through the ___ root of the spinal nerves.

A

dorsal

dorsal

66
Q

neural crest contributes to what part of the PNS

A

sensory neurons

autonomic neurons

enteric neurons

67
Q

The sensory components of the ___ originate from cells derived from the neural crest and the ectodermal placodes that aggregate outside the brain.

A

cranial nerves

68
Q

The sensory components of the cranial nerves

these collections of nerve cells bodies are called ___. These are functionally similar to the spinal (dorsal root) ganglia in the trunk.

A

sensory cranial ganglia

69
Q

In general, ___ of the cranial nerves send out two branches, one that enters the brain and one that is connected to a specific peripheral sensory organ

A

sensory ganglia

70
Q
A

MY= Myelencephalon

MT= Metencephalon

MS= Mesencephalon

OV= otic vesicle

ED= endolymphatic duct

71
Q

defects in the formation of NC and its derivatives

A

Neurocristopathies

72
Q

3 neurocristopathies

A

Result of defects in neural crest cells themselves but also of defects in the environment through which they migrate.

Defects affect only a single derivative of the neural crest, whereas other defects result in a wide array of seemingly unrelated clinical manifestations.

Frontonasal dysplasia= (craniofacial deformities)

DiGeorge syndrome= (craniofacial and conotruncal heart defects).

Waardenburg-Shah syndrome (and Hirschrung’s disease)= (hypopigmentation and aganglionic megacolon) Endothelin B receptor mutations (mice)

  • Lethal white syndrome (horses)*
  • Hypopigmentation and deafness (Dalmations)*
73
Q

DiGeorge Syndrome

A

Rare congenital disease (1:4,000 live birth).

caused by large deletion in chromosome 22- Tbx1 not formed correctly

Symptoms :

  • congenital heart defects; VSD (ventricular septal defect)- cardiac neural crest cell
  • craniofacial facial malformation (cleft palate)- cranial neural crest cell
74
Q

Waardenburg-Shah syndrome

A

pigmentation defects (white streak in hair) and deafness. (trunk neural crest cell issue)

Hirschsprung’s disease: absence of enteric neurons in the distal portion of the colon (aganglionic megacolon), congenital megacolon is occurring in approximately 1:5000 live births; (issue with sacral neural crest cells)

75
Q

Hirschsprung’s disease:

A

absence of enteric neurons in the distal portion of the colon (aganglionic megacolon), congenital megacolon is occurring in approximately 1:5000 live births; (issue with sacral neural crest cells)

issue with endothelin B receptor gene

“balloon man”

76
Q

Lethal white syndrome

A

•Affected foals are born after the full 11-month gestation and externally appear normal (but with DISTINCT coloration – all white coats, blue eyes

Have a nonfunctioning colon, develop colic and die within days

Mutation in the endothelin-B receptor gene causes lethal white syndrome when homozygous

Horses heterozygous for the mutation may exhibit a white-spotting pattern called “frame”.

77
Q

Hypopigmentation and deafness in Dalmatians

A

•There is a strong association between pigmentation defect and deafness in Dalmatians.

Defective cell type is the neural crest-derived melanocytes

•Melanocytes are present in normal hearing tissue (intermediate cells), but absent or reduced when deafness occurs.

Melanocytes help control the endocochlear potential which is required for normal hearing.

78
Q

adult neural crest stem cells

A

self-renew and can give rise to thousands of neurons, glia and smooth muscle cells

been identified in the peripheral nervous system of adult animals.

•Identified in rat sciatic nerve and gut.

79
Q

___ and ___ have an early role in specifying the identity of cell types along the dorsoventral axis of the spinal cord, but as development proceeds, more specialized cell types are generated.

A

Shh and BMP proteins

80
Q

___ in the developing spinal cord can be subdivided on the basis of the position at which their cell bodies are located, and by their axonal projection pattern.

A

Motor neurons

81
Q

Median motor column is found

A

along the entire spinal cord

project their axons to axial muscles

82
Q

Lateral MC medial

A

project their axons to ventral limb muscle

83
Q

Lateral MC lateral

A

project their axons to dorsal limb muscle

(lateral-lateral motor column)

84
Q

column of Terni

A

project their axons ventrally (sympathetic neurons)

85
Q

Subclasses of motor neurons are organized into longitudinal columns that occupy distinct, and in some cases, discontinuous domains along the ___ axis of the spinal cord.

A

rostrocaudal

86
Q

•Columnar subclasses of motor neurons can be distinguished by the combinatorial expression of the ___of transcription factors.

A

LIM family

87
Q

What class of molecules control the expression of molecules involved in the guidance of motor axons along different pathways to their specific targets in the periphery?

A

LIM family

88
Q

Within each motor column, motor neurons are further subdivided into ___, each innervating a specific muscle in the limb.

A

pools

89
Q

How are the subtype identities of motor neurons established?

A

we don’t know

maybe signal from the notochord?

90
Q

A functional ___ depends not only on the differentiation and positioning of specialized neural cells, but also on the specific connections these cells make among themselves and their peripheral targets.

A

nervous system

91
Q

•___ at the tip of the extending axon is the major force in guiding it to its destination.

A

Growth cone

92
Q

•In general, the growth cone moves in the direction where its ___makes the most stable contact.

A

filopodia

•Filopodia (microspikes) - slender cytoplasmic projections; extend beyond the leading edge of lamellipodia in migrating cells. They contain actin filaments cross-linked into bundles.

93
Q

___: slender cytoplasmic projections; extend beyond the leading edge of lamellipodia in migrating cells. They contain actin filaments cross-linked into bundles.

A

Filopodia (microspikes)

94
Q

4 guidance mechanisms for axons

A

long range:

chemoattraction (netrins)

chemorepulsion (samaphorins)

short range

contact attraction (cadherins)

contact repulsive (ephrins)

21 fall: Dev Bio (21 decks)

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