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23 Cards in this Set

  • Front
  • Back

Neural tube defects

X anterior neuropore closure ->anencephaly


X posterior neuropore closure -> spina bifida:


- occulta (benign, seen on X-rays)


- meningocele (meninges + CSF)


- meningomyolocele (... + spinal cord)


- rachischisis (spinal cord exposure)


=> SC/nerve roots dmg -> LE & bladder dysfx

Neural crest -> neuronal cells

Cells at the lip of neural tube closure =>


all of PNS (-somatic & preganglionic ANS):


- DRG & all sensory n's (-optic n, CN II)


- CN ganglia


- autonomic ganglia (also gut)


- adrenal medulla

Neural crest -> non-neuronal cells

- Schwann cells & satellite cells


- leptomeninges (pia, arachnoid)


- bone & CT of face & skull

Neural tube initiation

Ectoderm -> BMP -> ectoderm


Notochord -> noggin, chordin, folistatin --| BMP => neuroectoderm

Ventral vs. dorsal neural tube differentiation

Dorsal - neural crest (-> alar plate -> d. horn):


TGF-β: BMPs, dorsalin, Vit A, RA, noggin




Ventral - notochord (-> basal plate -> v. horn):


Shh, chordin, RA, noggin

Sonic Hedgehog as a ventralizing factor

PTC --| SMO




Shh -> PTC (R) => SMO -> Gli (TF's)




- cholesterol attached to N-term. -> cleavage => proper fx of A-terminus (X statins!)


- ventralizing activity demonstrated by extra NC


- defects -> holoprosencephaly

Neuron organization w/in spinal cord

(Dorsal/lateral)


Somatic sensory n's


Visceral sensory n's


----- sulcus limitans -----


Visceral motor n's


Somatic motor n's


(Ventral/medial)

RA -> ?

Concentrated in cervical area;


determines caudal identity w/ diffusion


-> activates TFs -> Hox genes regulation


=> rhombomere ID

Fate of neural tube vesicles

Optic -> retinas of eyes


Telencephalic -> lateral ventricles


Diencephalic -> 3rd ventricle


Mesencephalic -> cerebral aqueduct


Metencephalic & myelencephalic -> 4th ventricle




Metencephalon, 4th ventricle -> cerebellum

Vertebrate neuroepithelium divisions

1-cell layer thick neural tube walls, connected w/ both lumen & pial surface




-> Pial surface: S-phase


-> Neural tube lumen: M-phase (mitosis)


-> repeat

Neuroblast cell division

Cell surface signaling molecules:


notch-1 (apical) & numb (basal)




Vertical division -> equal


Horizontal division -> ↑ notch => post-mitotic -> differentiation => neurons & glia on pial surface (mantle zone)

Lateral inhibition in neural differentation

Notch + adjacent delta --| neurogenin (-> delta)




↓ notch -> ↑ neurogenin =>


- ↑ delta --| neurogenin in adjacent cells -> glioblasts


- helix-loop-helix genes -> neuroblast

Formation of layers of neural tube

Postmitotic cells:


ventricular zone -> mantle zone (gray matter); axons:


-> periphery = marginal zone (white matter)

Migration via cell-cell interaction

Radial glia: ventricular -> pial surface




- neuroblasts crawl along


(ex.: -> pial surface = cortex)

Migration of cortical neurons

Order of migration - inside-out:


Layer I = marginal zone (closest to pial surface) [Cajal-Retzius cells secrete reelin -> migration]


Layer VI (stays closest to ventricular zone)


Layer V -> b/w I & VI


Layer IV -> b/t I & V, etc.


Layer III


Layer II (ends by 16th w)

Processes of neural development

Mitosis & proliferation


Migration


Differentiation


Synaptogenesis


Apoptosis


Synaptic rearrangement/plasticity