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58 Cards in this Set

  • Front
  • Back
Cleavage and Blastocyte formation
Oocyte- zygote- 4 cell- 8 cell- morula (16 cell)- blastula
Inner Cell Mass
~ hypoblast (outer)
~ epiblast (inner)
becomes amniotic sac
becomes yolk
2 layers of embryo become 3
1)primitive streak forms in amniotic sac- axis of embryo, dorsal/ventral, anterior/posterior
2) epiblast cells migrate to primitive streak & displace hypoblast
3) Primary germ layers formed by epiblast cells
- 1 endoderm
-2 mesoderm
-3 ectoderm
4) notochord formed out of mesoderm cells just below primitive streak
ectoderm to neural tissue
1) Thickening of neural tissue-- neural plate
2) Neural groove/ neural folds formed on either side
3) Neural folds--neural crest
4) Neural tube is formed --ventricles brain spine
5) Neural crest cells-- PNS
Notochord sits below neural tissue and "tells" it to thicken
Formation of brain vesicles
1) Neural tube formed- allows for cell division& formation
2)Prosencephalon-- forebrain
Mesencephalon-- midbrain
Rhombencepalon-- hindbrain
3) Then...
Forebrain-- telencephalon/ diencephalon
Midbrain-- mesencephalon
Hindbrain-- metencepalon/ myelencephalon
Production of brain cells
Initially in lining of neural tube, in ventricular zone
3 layers form-- ependymal, mantel, marginal
Stem Cells
come from blastocyte stage
multipolar-- either glial or neural
Glial-- become asterocytes or oligodendrocytes
Neural-- become neurons
Secondary Cell Birth Area
cerebellum-- after fully grown, stops
hippocampus/ olfactory cells-- form new cells
subventricular zone
Neuronal Migration
new neurons travel down radial glial cells
use chemical stim
tissue layers form inside out
Neuronal Maturation
1) Dendritic arborization
2) Axon Extension
~Filopodia on Growth Cone
~ F-actin allows them to move
3) Axon guidance
~growth cone reaches to target cell through concentration gradient (high-low)
growth cone follows chemical released by target cells
Synaptic Pruning
More synaptic connections are created than needed
~ based on experiences, some stay, some go
1) occurs last, especially in frontal cortex
2) oligodendrocytes send out processes to axon, and wrap themselves around
~~ spaces called nodes
Formation of Neural Plate
*look at previous slides up to gatrulation
1) primitive pit (aka primitive node, organizer, spemenn's organizer, hensens node)
Mesoderm formation
the notochord also forms
--the cells above the notochord, are told to become the neurveous system
From Notochord
chemical signals are released
then fade
this allows the ectoderm on top to form the nerve cord
Search for Neural Inducers
embryo treated with lithium-- hyperdorsolized embryo occurs
embryo treated with UV rays-- no NS
Took UV embryo and treated it with mRNA from lithium embryo-- created rescued NS
Primitive Pit Example
in frogs
took 1 blastopore from one frog and put it on host blastula-- formed 2 complete NS
implies, organizing signal that tells cells passing through primitive node to become the NS
Neural Inducers
Bone Morphogenic Protein 4
--induces epidermal gene expression
--released by mesoderm as a whole
Noggin/ Chordin
secreted by notochord
block Bmp4 to inhibit binding wich induces neural tissue to form
no matter where notochord is placed, neurvous tissue will occur
Establishment of Spatial Axes
Dorsal/Ventral Patterning
Gradient of Sonic Hedgehog (Shh)
Gradient of Bmp4 antagonist
Establishment of Spatial Axes
Right/ Left Patterning
Cilia in Node establish right and left flow
-Morphogen has high concentration on right side
Gene expression differs on right & left
--Snail-- Right
--PitX2-- Left
Establishment of Spatial Axes
Anterior/ Posterior Patterning
Noggin/ Chordin-- anterior
Wnt-- posterior
Spemann's Experiment with Spatial Patterning
early signal produces 2 brains
late signal produces 2 posterior ends
embryos are first exposed to anterior signal (Noggin/Chordin)
later exposed to posterior signal (Wnt)
Do divide indefinitely in body-- outside body, they act strange and die
~can become any somatic cell
~have both X chromosomes active still
Embryonic Stem-Cells (ESC's)
created by inner cell mass of blastocyst-- become pluripotent stem cell
--can be neural, cardiac muscle, or blood cell
Epiblast Stem Cells
have already undergone X chromosome inactivation
Embrionic Germ Cells
either egg or sperm
Adult (somatic) Stem Cells
in bone marrow
in skin
in brain (hipp, sub-ventricular, olfactory)
Shape and Change
Neural plate elongates due to change in shape of cells
Folding = primary neurulation
Medial hinge points form (neural groove and fold)
Dorsolateral hinge points form
Convergence and Closure
Requires cell adhesion molecules (NCAM) and cell recognition molecules
Closures in 2 directions form cranial and caudal neuropores
Dorsal-Ventral Patterning
(Hind and Spine)
at this point, the neural tube as fairly undifferentiated cells
~Dorsal-- roof plate
~Ventral-- floor plate
-- roof, sensory neurons
-- floor, motor neurons
sulcus laminus lines inside
located below floor plate
-- if removed, no floor plate, ONLY dorsal structures
-- if transplanted, enduce ectopic motor neurons
Notochord Shh---- clearly, Shh involved in ventral structures
Dorsal Structures
induced by Bmp4 and Bmp7
~expressed by epidermal cells
Ventral Structures
Shh expressed in notochord THEN floor plate
Dorsal-Ventral--> Anterior Region
median-ganglionic eminence
lateral-ganglionic eminence
caudal-ganglionic eminence
~ all 3 large grouping of cells that then migrate
Ventral structures
induced by Shh
~ expressed by mesoderm
Dorsal Structures
induced by Gli3
Dorsal--sensory cortex
Anterior-Posterior Specification
formation of Rhombomers
collection of cells
all cells within 1 rhombomer wil serve a specific function together
segmented pattern determined by HOX gene
HOX gene
found in fruit fly
absolute segmentation in HOX (direct segementing)
Cerebellum arises from Rhombomers
Retinoic Acid
contributes to anterior posterior patterning
High concentration posterior
degraded in anterior
secreted by paraxial mesoderm
Influences HOX gene expression by gradient or timing
derivitive of Vit A
boundry between tectum and cerebellum
Prosomeric Model of Forebrain Development
Not as organized as Rhombomer
Early Patterning of cerebral cortex
established by differential expression of Emx2 and Pax6
~these inhibit one another to promote specification
Large motor
Shrunk visual
Large visual
Shrunk motor
Before neural tube closure-- Induces Ventral structures
After neural tube closre--
Induces dorsal sturctures
Noggin/ Chordin/ Fillostatin
Inhibits Bmp4
Promotes anterior structures
Induces anterior structures
e.g. hindbrain/ spinal cord
Induces Ventral structures
Gene expressing trans. factor
induces neurons in Rhonbomere sequence
Ritonoic Acid
derivitive of Vit. A
induces posterior structures
Induces Posterior sturctures
e.g. visual cortex
Induces Anterior structures
e.g. motor cortex