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83 Cards in this Set

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Neural induction
Conversion of ectoderm into neuroectoderm during gastrulation
Neurulation
Formation of the neural tube under the influence of notochord
Pial surface
Surface of the neural tube facing OUT
Ventricular zone
Region of neural tube near the lumen; area of cell mitosis; aka the APICAL region.
Where are secondary germinal zones located?
In more basal (outer) regions
What are cells like at the BLASTULA stage?
-All totipotent
-Prepatterned - organized in layers
What does totipotent mean?
It is fated to give rise to a certain tissue, but has the capacity for differentiation.
What does the regionalization of blastula cells allow?
Allows them to be FATE-mapped.
What is Gastrulation?
The involution/invagination of cells which forms the neural tube.
What happens to the blastula cells during the process of gastrulation?
They become fated to one of the three dermal tissue cell types:
Endoderm, ectoderm and mesoderm.
What axis develops first, and what follows?
First = Anterior/posterior
Later: Dorsal/ventral
What develops faster? A or P?
Anterior
What has to occur before neurulation can take place?
Establishment of the Neural Plate
What is Neurulation?
The process of convergence of ectodermal neural plate cells in the midline to form a tube.
What does the formation of the notochord do during neurulation?
Gives the dorsal/ventral patterning of the spinal cord.
What are the early Regional specializations of the neural tube?
-Prosencephalon
-Mesencephalon
-Rhombecephalon
What does the Prosencephalon morphologically differentiate into?
Telencephalon
Diencephalon
What does the Mesencephalon morphologically differentiate into?
Mesencephalon
What does the Rhombencephalon morphologically differentiate into?
Metencephalon
Meyelencephalon
What axis of development does the regional differentiation of the neural tube give rise to?
Anterior/posterior
What are the embryonic flexures that arise during NS development?
Cephalic flexure - between the midbrain and hindbrain.
Cervical flexure - between the hindbrain and spinal cord
What is a 3rd flexure that develops later?
Pontine flexure - between the other two flexures.
What are the tiny microflexures that develop in the hindbrain called?
Rhombomeres
What do Rhombomeres give rise to?
Molecular differentiation under the influence of the HOX code transcriptional network.
What is the approximate time period that neurulation and development of the NS is occuring?
50 - 100 days old.
So what are the components of the CNS at the 3-vesicle stage?
1. Forebrain (Prosenceph)
2. Midbrain (Mesenceph)
3. Hindbrain (Rhombencph)
(caudal part of neural tube too)
What are the components of the CNS at the 6-vesicle stage?
Telenceph/Dienceph
Mesenceph
Metenceph/Meyelenceph
Caudal part of neural tube
What does the Telencephalon give rise to in the adult CNS?
1. Cerebral cortex
2. Basal ganglia
3. Hippocampal formation
4. Amygdala
5. "Olfactory bulb
What does the Diencephalon give rise to in the adult CNS?
1. Thalamus
2. Hypothalamus
3. Subthalamus
4. Epithalamus
5. Retina
6. Optic nerves/tracts
What does the Mesencephalon give rise to in the adult CNS?
The midbrain
What does the Metencephalon give rise to in the adult CNS?
The pons and cerebellum
What does the Meyelencephalon n the adult CNS?
The medulla
What arises from the caudal part of the neural tube?
The spinal cord
What does the term "FLOOR PLATE" refer to in the neural tube?
The ventral midline region - the basal plate.
What does the term "ROOF PLATE" refer to in the neural tube?
The dorsal midline region - the alar plate.
What divides the dorsal and ventral parts of the spinal cord?
The sulcus limitans.
What is the Dorsal Horn?
The region of the spinal cord dorsal to the sulcus limitans.
What is the Ventral horn?
The region of the spinal cord ventral to the sulcus limitans.
What is the type of cells that remain in the sulcus limitans region?
Ependymal cells
What TYPE of cells form the neural tube?
Pseudostratified epithelial cells
At which side of the Pseudostratified epithelialium of the neural tube are the nuclei of dividing cells located?
At the APICAL side / LUMEN / Ventricular Zone
What process do proliferating cells in the developing spinal cord undergo?
Interkinetic Nuclear Migration
What occurs during interkinetic nuclear migration?
The nucleus of the cells moves in relation to its progression through the cell cycle.
Where does the cell nucleus move during the G1-S portion of the cell cycle?
From apical to basal
Where does the nucleus move during the S-G1 portion of the cell cycle?
Back to the apical zone.
What is the PURPOSE of interkinetic nuclear migration?
To allow mitosis to occur only near the ventricular zone.
What are junctional complexes?
Tight junctions between the pseudostratified epithelial cells at the APICAL side
What are the features of the neuroepithelial cells at their BASAL side?
Endfeet which contact the basement membrane.
So where does DNA synthesis (S phase) occur in neuroepithelial cells of the neural tube?
At the BASAL side
Where does M phase occur?
At the APICAL side in the ventricular zone.
What areas develop as the Dorsal-Ventral axis of the spinal cord differentiates?
Alar plates and Basal plates
What type of neurons developm from the Alar plates?
Interneurons
What type of neurons developm from the Basal plates?
Motor neurons
What are the 6 zones that initially develop in the CEREBRAL CORTEX?
1. Ventricular zone
2. Intermediate zone
3. Preplate
4. Subplate
5. Cortical plate
6. Marginal zone
What is the Ventricular zone?
The zone near the lumen of the neural tube; Area of cell mitosis.
What is the ventricular zone also called?
-Ependymal layer
-Germinal zone
What is the Intermediate zone?
Separates the ventricular zone from the preplate.
What does the Intermediate zone contain?
Axons of Preplate neurons EXITING the cortex, and axons of Thalamic neurons ENTERING the cortex.
What is the Preplate?
A region that eventually splits to form the subplate and the marginal zone.
What forms the Preplate layer?
The fist post-mitotic cortex neurons.
What is the Subplate?
Splits off from the Preplate; TRANSIENT neuron population that has inmportant functions in signalling development of the outer cortex layers.
What is the Cortical plate?
A zone formed by cells migrating from the Ventricular zone; the plant themselves between the 2 derivatives of the preplate.
What does the cortical plate zone separate?
The Subplate from the Marginal zone (both derivatives of the preplate).
What does the Cortical plate do?
Gives rise to the Cortex layers 2-6
What is the marginal zone?
-Outermost layer of cortex that contains neuron processes -WHITE MATTER
-Gives rise to Cortex layer 1 -Derivative of the Preplate
In what direction do cells migrate during Cortex Development in the Cerebrum?
ONLY RADIALLY - from the apical ventricular zone to basal zone.
In what direction do cells NOT migrate during Cerebral Cortical development?
Tangientially - there is no lateral movement like anterior to posterior; only from inside lumen side to outside pial/basal side.
What directs the migration of cells during cortical development of the cerebrum?
Radial Glial cells - their fibers
What is the first zone of the cerebral cortex to develop by migration?
The Preplate zone
In what ontological manner (birthdate) does cortical neurodevelopment occur?
Inside-first (Ventricular)
Outside-last (Marginal)
How does Histogenesis in the cerebral cortex compare to that of the Retina?
Opposite; Cerebral cortex grows inside-first, outside-last; where the Retina differentiates in a jumbled manner.
When do cortical neuroblasts become RESTRICTED to a particular laminar cell fate?
At S-phase of their last cell cycle. Prior to that, they can be re-specified if transplanted into an older embryo cortex.
What is the order of layer formation in the cerebral cortex?
1. Ventricular zone
2. Preplate
3. Intermediate zone
4. Subplate
5. Cortical plate
6. Marginal zone
What are 2 ways in which the development of CEREBELLUM cortex vastly different from Cerebral?
1. It exhibits BOTH Radial AND Tangiential (lateral) migration.
2. It develops a SECONDARY germinal zone.
What develops from the primary, apical Ventricular zone?
(3 things)
1. Deep cerebellar nuclei cells
2. Purkinje cells
3. Golgi cells
What develops from the secondary germinal zone, the External granular layer? (3 things)
1. Granule cells
2. Basket cells
3. Stellate cells
What does the secondary EGL arise from?
The rhombic lips - proliferative cells that have migrated over the rhombic lips.
Where is the secondary EGL located?
Above the developing cerebellum near the pial surface.
At what time period does the cerebellar cortex develop?
60-90 days
In what direction do cells in the EGL develop?
Basal to Apical (as opposed to the normal apical to basal pattern).
How does the EGL develop?
1. Lateral migration over the Rhombic lips (Tangential)
2. Radial migration down into the apical side of the developing cerebellum.
What guides the radial migration of EGL cells into the granular layer?
Bergmann cells
What are Bergmann cells similar to?
Radial glial cells in the cerebral cortex - but they cause migration in the oppisite direction, from Basal to Apical.