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71 Cards in this Set

  • Front
  • Back
What is the Neuroepithelium?
The organized epithelial cells that make up the neural tube.
What cell cycle phase are cells with nuclei next to surface of NT in? Next to Lumen?
Surface: S phase - duplicating

Lumen = M phase - dividing
The spinal cord wants how many layers ultimately? What is each layer called? What does it consist of?
-Ventricular: ependymal cells
-Intermediate: neuroblasts
-Marginal: axons
What is the order of forming the spinal cord cells?
Neurons - form first
Glial cells - second
Ependymal cells - last
How do neurons form? (3 steps)
1. Neuroblasts are born
2. Migrate beyond dividing cells (lumen) to NT exterior
3. Differentiate into neurons
What do Glioblasts develop into?
Astrocytes and Oligodendrocytes
What are Astrocytes + Oligodendrocytes called?
Macroglia - support cells of CNS
What are Radial Glia?
Special glial cells that guide migration of neuroblasts and glioblasts; temporary.
What cells form last in the spinal cord formation?
What is the fate of ependymal cells?
They become epithelial cells lining the ventricles
What are Microglia?
Macrophages that migrate into the CNS with blood vessel sprouts
What are microglia derived from?
What does neuron and glial formation result in?
Trilaminar layer:
-Ventricular (inner)
-Marginal (outer)
Which layer expands as a result of neuron and glial formation?
What 4 structures develop in the intermediate layer?
1. Alar plate
2. Basal plate
3. Sulcus limitans
4. Roof and Floor plates
What is the Alar plate?
Sensory neuron columns in the dorsal half of the intermediate layer
What causes the Alar plates to form?
Dorsalizing signals
What forms in the Ventral lateral half of the intermediate layer?
Basal plates
What are the Basal plates?
Motor neuron columns
What causes the Basal plates to form?
Ventralizing signals
Groove that runs entire length of spinal cord and forms a boundary between motor and sensory areas:
Sulcus limitans
What forms at the Roof and Floor plates?
Nothing - there is no intermediate layer here.
What is Spinal cord vertebral length at
-8 wks
-24 wks
8 wks: entire length to coccyx4
24 wks: extends to S1
Birth: L3
Adult: L1/L2
How does the brain form?
By the flexing of the neural tube
What 3 flexures develop in the neural tube? In what direction is flexing?
Mesencephalic/midbrain: Ventral
Cervical: Ventral

Rhombencephalic/pontine: Dorsal
Where is the Cervical flexure in relation to adult?
At the brain/spinal cord junction
What does the Rhombencephalic flexure eventually cause?
The brain to fold back on itself because it is a dorsal flexure
What is filum terminale?
Leftover pia mater as the spinal cord regressed.
3 brain regions visible at the open neural fold stage of CNS devo:
-Prosencephalon = forebrain
-Mesencephalon = midbrain
-Rombencephalon = hindbrain
What are the 3 brain regions named in reference to?
-New made Mesencephalic flexure
Pros = before it
Mes = at it
Romb = after it
Where is the rhombencephalic flexure in relation to mesencephalic and cervicals?
Between them.
What does the Prosencephalon subdivide into? What will each become?
-Telencephelon (endbrain) - will become cerebral hemispheres
-Diencephalon - thalamus/retina
What does the Mesencephalon subdivide into? What will it become?
Becomes various nuclei
What does the Rhombencephalon subdivide into? What will each become?
Cranial 1/2 - Metencephalon; Will form CEREBELLUM and Pons.
Caudal 1/2 - Myelencephalon; Will form Medulla Oblongota
What plays a role in the proper location of cranial nerves?
What is Holoprosencephaly?
Failure of the prosencephalon to regionalize
What are the visual defects that result from holoprosencephaly?
Midline and facial malformations
What part of the brain is primarily by holoprosencephaly?
Forebrain - Corpus callosum, olfactory tract, falx cerebri may be absent; single ventricle
How far up the spinal cord does the sulcus limitans extend?
To the Mesencephalon
How far up do Basal and Alar plates form?
Through brain stem but not into forebrain
What develops in the brain stem
-Alar plates
-Basal plates
Alar = CN sensory nuclei

Basal = CN motor nuclei
What develops in the marginal layer of the brain stem?
Nerve tracts to connect brain regions to each other
What does the lumen of the NT become? What special structure does it contain?
The ventricular system - Choroid plexus in the roof of each.
What is the Cerebellum derived from?
Bilateral, dorsal outgrowths of Metencephalon - Rhombic Lips
What does fusion of the Rhombic Lips form?
Cerebellar Plate - VERMIS
In what order do the structures of the cerebellar cortex form?
1. Neuroblasts from Intermed layer - Extrnl Granular layer
2. More migrate - Purkinje layer
3. End of fetal period, granular cells move back to form the real granular layer
So what 3 layers result in the Cerebellum Cortex?
1. External Granular
2. Purkinje
3. Granular
Deep Nucleus innermost
When do the Cortexes develop?
Week 5
What 2 structures are in the Cerebral Hemispheres?
1. Cortex (external)
2. Corpus striatum (internal)
aka basal ganglia
What do the Cerebral hemisphers grow out of?
How do the layers of the cerebral cortex form?
1. Cortical plate - neuroblasts migrate out into marginal layer
2. Fetal period into childhood, Cortical plate -> 6 layer cortex
Increased Neuron PROLIFERATION results in:
Decreased Neuron PROLIFERATION results in:
Which is worse?
Micro - accompanied by severe mental retardation, where megalo may not have any.
3 Diseases of Error in Neuron MIGRATION:
1. Lissencephaly
2. Micro/macrogyria
3. Agenesis of Corpus Callosum
What is the visible result of lissencephaly?
No gyri - smooth cortex
What is the visible result of Micro/macrogyria?
Many or large gyri
What is the least severe defect of neuron migration?
Corpus callosum agenesis - can be asymptomatic.
What is hydrocephalus?
Enlarged head due to blockage of the ventricular system flow of CSF
2 types of hydrocephalus:
Non-communicating Hydrocephalus:
CSF can't get into subarachnoid space b/c it is blocked at Cerebral aqueduct
Another name for noncommunicating:
Communicating Hydrocephalus:
CSF CAN get into subarachnoid space, but CAN'T get into Arachnoid granulations (so no resorption can occur)
Another name for communicating:
What is a 3rd type of hydrocephaly? What is it?
Arnold-Chiari malformation
-Caudal displacement/herniation of cerebellum
What often accompanies Arnold-Chiari malformation?
Myelomeningocele, Myeloschisis, or Syringomyelia
At what spinal cord level is
-Sympathetic fibers
-Parasympathetic fibers
Sympathetics = T1-L2

Parasympaths = S2-S4 & Brainstem
What are the 3 precursors of the peripheral nervous system?
1. Neural crest
2. Ectodermal placodes
3. Spinal cord and brain
What does Neural Crest become in the PNS?
-Primary sensory neurons
-Schwann cells
-Postganglionic autonomic neurons
What do Ectodermal Placodes contribute to the PNS?
Sensory ganglia of cranial nerves 5, 7-10
What do the Spinal cord and Brain form?
-Axons of motor neurons
-Axons of preganglionic symp and parasymp neurons