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30 Cards in this Set

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From what germ layer does the NS arise?
Ectoderm
What is the default state of ectodermal cells?
Neuronal Tissue - but release factors telling neighbors NOT to be N.S.
How does Neural tube form?
See notes
What are the 4 neural tube closure defects?
1. Spina Bifida

2. Meroanencephaly

3. Anencephaly

4. Exencephaly
What is a defect in the vertebral arch formation or neural tube closure resulting in an exposure and possibly extrusion of the spinal cord and its surrounding tissues?
Spina Bifida
What is a defect in cranial neural-tube closure that results in partial absence of the brain

Most common tube defect
Meroanencephaly
What is a defect in cranial neural tube closure that results in complete absence of brain?
Anencephaly
What is a defect in cranial neural tube closure that results in exposure and possibly extrusion of brain?
exencephaly
What are the 3 vesicles seen in the broad cranial end of the neural plate at week 4?
1. Forebrain

2. Midbrain

3. Hindbrain
What are the 5 vesicles seen in week 5?
Telencephalon, Diencephalon (forebrain)

Mesencephal (Midbrain)

Metencephalon, Myelencephalon (hindbrain)
What are the 9 special subdivisions of the hindbrain called?
Rhombomeres
What is the purpose of hox genes?
Specify segmental identity along the Anterior/Posterior axis
What defines specific rhombomere segmental identify?
A combinatorial Hox code - giving different TF's
What important nerves emerge from specific rhombomeres?
Cranial nerves (except CN I - IV??)
Generally, what patterns the dorso-ventral axis in the neural tube?
Localized inductive cues
What is the role of floor plate in D-V patterning?
Secretes signals to instuct VENTRAL cells to acquire specific fates:

Sonic Hedgehog (SHH)
What is the role of roof plate in D-V patterning?
Secretes other signals to instruct DORSAL cell fates

Bone Morphogenic Proteins (BMPs)
What does the notochord induce?
The floor plate
How, cellularly, does SHH help pattern the NT?
Different concentrations of SHH induce different TF's

Specific pairs of TF's determine cell fate
What is a defect in the bifurcation of the forebrain, resulting in a single hemisphere?
Holoprosencephaly
What is one main cause of holoprosenchephaly?
Loss of SHH signaling
What is neural crest cell fate largely determined by?
LOCATION (therefore can transplant them) that gives different external cues
How do neurons assume specific identities?
Different combination of signals, presumably similar to those present at particular locations in embryo, induce different cell fates
How are the cortical layers developed?
INSIDE-OUT maturation

- new neurons migrate past older layers
How do axons find their appropriate targets?
Guidance Cues that are differentially localized
What is it called when a patient can't look side to side?
Horizontal gaze palsy
What is horizontal gaze palsy caused by?
Disruption of robo-3 gene
What are a family of extracellular signaling molecules that promote the survival of specific neurons?
Neurotrophins
How does cell survival depend on target aquisition?
Post-synaptic cells (target) secretes TROPHIC FACTORS that are required for neuronal survival
What happens to neurons that do not receive enough Neurotrophic Factors?
They die via apoptosis