test 2 lecture 18 -19 nervous system Flashcards
1
Q
The trilaminar embryo (aka trilaminar blastocyte) has three distinct layers
A
- ectoderm
- mesoderm
- endoderm
2
Q
The central and peripheral nervous systems are entirely derived from the ___ layer.
A
ectoderm
3
Q
The development of the central and peripheral nervous systems is initiated by the induction of the ___ (occurs during gastrulation).
A
neural plate
4
Q
___ is the the process by which neural plate is generated from ectoderm
A
neural induction
5
Q
__ directs neural induction
A
notochord (part of mesoderm)
6
Q
ectoderm stays epidermal ectoderm by binding with ___
A
BMP4
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
8
Q
___ of BMP4 signaling in the ectoderm is required to convert the ectoderm into neural tissue (mediated by the dorsal mesoderm)
A
Inhibition
9
Q
Noggin, Chordin and Follistatin act as ___
A
BMP antagonists
bind to BMP protein and prevent BMP from binding to its receptors
10
Q
___ are secreted by the dorsal
mesoderm/notochord to stop BMP
A
Chordin, Noggin and Follistatin
11
Q
___ is the default state of the ectoderm
(in the absence of BMP4 signaling)
A
Neural fate
12
Q
transformation of the neural plate into the neural tube
A
Neurulation
13
Q
The nervous tissue induced by BMP4 inhibition is anterior in character (___).
A
forebrain
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
15
Q
The central nervous system is regionalized along the ___ axis.
A
anterior-posterior (AP)
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
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_
18
Q
What are the three posterior neural inducers
A
fibroblast growth factor (FGF) family,
Retinoic acid
Wnt-3a
19
Q
neurulation
A
neural plate transforming into neural tube
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
21
Q
The prospective brain is initially subdivided into three primary vesicles:
A
Forebrain (prosencephalon)
Midbrain (mesencephalon)
Hindbrain (rhombencephalon)
22
Q
• Forebrain (prosencephalon) becomes
A
23
Q
Midbrain (mesencephalon) becomes
A
24
Q
hindbrain becomes ___
A
25
\_\_\_ is the boundary between the midbrain and the hindbrain):
Isthmus
26
Isthmus
•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.
27
if Wnt 1 is inhibited what will happen to midbrain?
if FGF8 is placed somewhere else what will happen?
will not develop
2nd midbrain will develop but in wrong direction
28
•The hindbrain is divided into periodic swellings known as \_\_\_
rhombomeres.
29
•The ___ represent separate "territories", such that cells from one rhombomere cannot mix with cells from adjacent rhombomeres.
rhombomeres
30
In the hindbrain, ___ encode positional values along the anterior-posterior axis of the nervous system.
**Hox** genes
31
The identity of each \_\_\_is defined by the expression pattern (specific combination) of **Hox** genes.
rhombomere
32
It is unclear how **Hox** genes become activated at appropriate levels, although \_\_\_, \_\_\_, and ___ are likely regulators.
Retinoic Acid (RA)
Egr2
Mafb
33
how does retinoic acid effect hindbrain
**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
34
zones of neural tube
**marginal zone**: neuroblasts, glioblasts
**Ventricular zone**: neural stem cells
35
Neuroepithelial cells are the precursor cells for ALL of the cells in the CNS (with one exception). what is the exception?
**microglial cells**
immune cells of the CNS
these come from mesenchymal cells
36
neuroepithelium can turn into what two major types
glial lineage progenitor cells
neuronal lineage progenitor cells
37
glial lineage progenitor cells can turn into
ependymal cells- lining of ventricles
type 1 astrocyte
Type 2 astrocyte
oligodenrocytes
38
**_Astrocytes_**
come from gilial lineage progenitor cells
Supporting cells: give physical and metabolic support, can regulate neuronal activity
39
Oligodendrocytes
**schwann cells**
Myelinating cells: wrap axons with myelin, increasing speed of electrical transmission
40
neuronal lineage progenitor cells lead to
mature neuron
## Footnote
1,000-10,000 types; electrical activity executes all the functions of the nervous system
41
what can help orient ventral vs dorsal neural tube
group of non neural cells
## Footnote
**roof plate**
**floor plate**
42
notochord will cause what to form in the neural tube?
floor plate
motor neurons
43
The Notochord is the source of two inductive signals.
local signal that induces **floor plate** differentiation at the midline
long-range signal that induce **motor neurons** on each side
44
The \_\_\_, once induced, acquires the ability to generate both short- and long-range signals.
floor plate
45
Notochord secretes ___ to induce the formation of floor plate in the neural tube
sonic hedgehog Shh
46
After formation of the Floor plate of the neural tube, the floor plate will secrete ___ making a gradient
Shh (sonic hedgehog)
47
\_\_\_ acts as a morphogen to generate neuronal diversity
Shh
48
Graded amounts of Shh generate distinct populations of motor neurons and interneurons in the ___ portion of the spinal cord.
ventral
49
dorsal differentiation of neural tube is by
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 signa**l identity rather than signal intensity.
50
Neuronal diversity in the dorsal spinal cord is established as a result of a ___ identity rather than signal intensity.
**diversity in signa**l
loss of GDF7, a BMP related factor led to the selective loss of a single class of dorsal interneurons
51
diversity and pattern in the neural tube
**dorsal** by different signals
**ventral** by gradient of Shh
52
During neurulation, the neural crest is at the most ___ region of the neural tube
dorsal
53
•To migrate, neural crest cells will undergo \_\_\_
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
what are some things neural crest cells can turn into
55
Upon neural tube closure, neural crest cells delaminate in a \_\_\_and migrate along specific routes.
rostro-caudal wave
56
cranial neural crest cells turn into
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
cardiac neural crest cells turn into
septum of the outflow tract of the heart (separates the truncus arteriosus into the pulmonary artery and aorta) and wall of large arteries
58
neural crest induction
**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
The \_\_cells are a stem cell-like population. Some of these cells are multipotent which means \_\_
neural crest
are able to generate numerous cell types (bone, cartilage, smooth muscle, neurons, pigment cells)
60
neural crest diversification is dependent on local factors, an example is glial growth factor stimulates differentiation into \_\_\_, while endothelin-3 stimulates differentiation into \_\_\_
autonomic neurons
melanocytes and enteric neurons formation.
61
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 \_\_\_
neural crest cells
ectodermal placodes.
62
The cell bodies of these sensory cells are located ___ the central nervous system.
outside
63
The \_\_consists of cranial, spinal and visceral nerves and ganglia.
PNS
64
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.
neural crest cells
65
Spinal ganglia cell bodies project branches towards the \_\_\_part of the spinal cord through the ___ root of the spinal nerves.
dorsal
dorsal
66
neural crest contributes to what part of the PNS
sensory neurons
autonomic neurons
enteric neurons
67
The sensory components of the ___ originate from cells derived from the neural crest and the ectodermal placodes that aggregate outside the brain.
cranial nerves
68
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.
sensory cranial ganglia
69
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
sensory ganglia
70
MY= Myelencephalon
MT= Metencephalon
MS= Mesencephalon
OV= otic vesicle
ED= endolymphatic duct
71
defects in the formation of NC and its derivatives
Neurocristopathies
72
3 neurocristopathies
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
DiGeorge Syndrome
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
**Waardenburg-Shah syndrome**
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
**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)
issue with **endothelin B receptor gene**
“balloon man”
76
Lethal white syndrome
•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
**Hypopigmentation and deafness in Dalmatians**
•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
adult neural crest stem cells
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
\_\_\_ 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.
Shh and BMP proteins
80
\_\_\_ 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.
Motor neurons
81
Median motor column is found
along the entire spinal cord
project their axons to axial muscles
82
Lateral MC medial
project their axons to **ventral limb muscle**
83
Lateral MC lateral
project their axons to dorsal limb muscle
(lateral-lateral motor column)
84
column of Terni
project their axons ventrally (sympathetic neurons)
85
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.
rostrocaudal
86
•Columnar subclasses of motor neurons can be distinguished by the combinatorial expression of the \_\_\_of transcription factors.
LIM family
87
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?
LIM family
88
Within each motor column, motor neurons are further subdivided into \_\_\_, each innervating a specific muscle in the limb.
pools
89
How are the subtype identities of motor neurons established?
we don't know
maybe signal from the notochord?
90
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.
nervous system
91
•\_\_\_ at the tip of the extending axon is the major force in guiding it to its destination.
Growth cone
92
•In general, the growth cone moves in the direction where its \_\_\_makes the most stable contact.
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
\_\_\_: slender cytoplasmic projections; extend beyond the leading edge of lamellipodia in migrating cells. They contain actin filaments cross-linked into bundles.
Filopodia (microspikes)
94
4 guidance mechanisms for axons
**long range:**
chemoattraction (netrins)
chemorepulsion (samaphorins)
**short range**
contact attraction (cadherins)
contact repulsive (ephrins)
