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Flashcards in Lecture 2 Deck (31):
1

What is gastrulation? What are the parts?

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

2

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

3

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

4

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)

5

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

6

Where do neural crest cells originate?

Closure point of the neural tube

7

What structures come from neural crest cells?

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

8

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

SHH - made by notochord
Floor plate
Ventral
Motor

9

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

BMP
Roof plate
Dorsal
Sensory

10

What is the dividing line of the neural tube?

Sulcus limitans
Separates doral/ventral - sensory/motor

11

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

12

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

13

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

14

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

15

How do HOX genes pattern the brain?

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

16

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

17

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

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

18

What are the structures in the diencephalon?

Thalamus & hypothalamus

19

What structures are in the metenchepalon?

Pons & cerebellum

20

What structures are in the myelencephalon?

Medulla

21

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

22

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

23

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
Hydrocephalus

24

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

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

25

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

26

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)

27

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

Not/incomplete connection of corpus callosum

28

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

Getting a neural cell from 1 location to another
RADIAL patterning

29

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

30

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

31

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