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Flashcards in Lecture 2 Deck (31):

What is gastrulation? What are the parts?

Development of 3 layer embryo
1. Endoderm - invaginates first
2. Mesoderm
3. Ectoderm - nervous tissue!


What is the notochord? Describe how it forms.

Pre-notochordal cells start at the primitive node
Invaginate slide up the midline
Sits level with mesoderm, above endo, below ecto
Notochord = SOLID cord of cells, organizing center for NS development


How does the neural plate develop? What will the neural plate become?

Notochord sends signals into the ectoderm above that create neural plate
Neural plate --> neural tube


How many closure points are there for the neural tube? What are the diseases for each spot if there are errors?

1. Closure at cervical region (craniorachischisis)
2. Closure @ caudal neopore (spina bifida)
3. Closure @ cranial neopore (anencephaly)


What are the 3 variants on the spina bifida spectrum?

SB occulta = open vertebral arch
- Look for hairy patch!
SB cystica:
a. Meningocele = cyst of CSF + meninges
- Easy surgical removal
b. Meningomyelocele = cyst contains neural tissue, problematic


Where do neural crest cells originate?

Closure point of the neural tube


What structures come from neural crest cells?

All of PNS: DRG, sympa chain ganglia, enteric NS
Melanocytes, adrenal medulla, cardiac valves
Cranio-facial skeleton


What transcription factor patterns the neural tube FLOOR plate? Will this be dorsal or ventral? Sensory or motor?

SHH - made by notochord
Floor plate


What transcription factor patterns the neural tube ROOF plate? Will this be dorsal or ventral? Sensory or motor?

Roof plate


What is the dividing line of the neural tube?

Sulcus limitans
Separates doral/ventral - sensory/motor


What determines radial patterning of the neural tube?

Division and migration of neuro-epithelial cells
Radial patterning = inside vs. outside

Stem cells start long - divide into 2 daughter cells
- 1 daughter stays
Other daughter shrinks and differentiates according to TFs to specific layer depending on end-cell type


What determines rostral/caudal patterning of the neural tube? What is the difference between rostral vs caudal factors?

HOX genes (order is important!)
Caudal = towards FEET, all HOX genes expressed
Fewer genes expressed moving toward rostral - towards head


What determines L vs R neural tube patterning?

Amounts of SHH to the L and R of midline determine medial vs lateral
More SHH = medial


What is holoprosencephaly? What error results in this condition?

Error in cranial lateralization
SHH deficiency leading to single (instead of mirror) facial and cranial structures


How do HOX genes pattern the brain?

Into 3 primary vesicles/swellings:
1. PROsencephalon = FOREbrain
2. MESencephalon = MIDbrain
3. RHOMBencephalon = HINDbrain


What the 3 bends that determine brain shaping?

Cervical flexure = bends brain anteriorly
Mesencephalic flexure = brings forebrain anterior
Pontine flexure = stacks cerebellum on top of brainstem


Name the secondary (adult) vesicles that arise from each of the 3 primary swellings.

Prosencephalon (forebrain) = tel & diencephalon
Mesencephalon = midbrain
Rhombencephalon (hindbrain) = met & myelencephalon


What are the structures in the diencephalon?

Thalamus & hypothalamus


What structures are in the metenchepalon?

Pons & cerebellum


What structures are in the myelencephalon?



How do the ventricles of the brain form?

Neural tube always had a hollow fluid filled canal
Will become the ventricles in the brain part - spinal canal in the spine part


How do the ventricles of the brain form?

Neural tube always had a hollow fluid filled canal
Will become the ventricles in the brain part - spinal canal in the spine part


What is a problem point during ventricle formation? What condition may result?

Cerebral aqueduct (connects 3rd and 4th V)
So thin - stenosis during development/life


What is the main driver of axon guidance during development? Name 2 specific structures.

1. Filopodia = finger projections that sample enviro around growth cone
2. Lamellipodium = base from which the filopodia come from


What are the general growth mechanisms acting on growth cones?

Chemoattraction (TOWARDS) & chemorepulsion (RETRACT)
- For long range cues (diffusable molecules)
Contact with short range cues like gradients or guidepost cells


What is a pioneer axon? Does the CNS or PNS use this method?

Creates axon scaffold for secondary axons
For both CNS (for central tract formation aka corpus callosum) & PNS (limbs)


What happens if you have defective axon guidance via pioneer axons? (specific defect in mind)

Not/incomplete connection of corpus callosum


What is neural migration? What processes is this important for?

Getting a neural cell from 1 location to another
RADIAL patterning


How do the cortical layers form?

Inside out!
L6 is the first to develop - then must migrate through all the other layers to get to the right place


What is tangential migration? What are 2 example paths?

LONG range neuron migration
1. Ganglionic eminence will give rise to ALL cortical inhibitory neurons - migrate from the center of developing brain to the cortex
2. Rhombic lip sends all its cells to the cerebellum/cerebral nuclei


Which sulci are the first to form? What happens if this doesn't happen correctly?

Central sulcus & lateral fissure! (the BIG 2)
Incomplete/lack of gyri/sulci if neuronal migration is defective in this respect