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NEUR3005 > Lecture 2 - embryogenesis > Flashcards

Lecture 2 - embryogenesis Flashcards

(46 cards)

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1
Q

The CNS is generated by what type of cells?

A

Pluripotent neuroepithelial stem cells (spindle-shaped)

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2
Q

Interkinetic nuclear migration

A

Early in the cycle > move superficially
Later > come down to deep surface (VZ)

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3
Q

After interkinetic nuclear migration…

A
  1. Neuroepithelial stem cells undergo mitotic division in VZ
  2. Then we get an increase in progenitor number
  3. Increase in size until a certain point
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4
Q

When proliferative zone has reached its limit…

A

Radial Glial cells appear (1st non-mitotic cells)

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5
Q

Radial Glial cells

A

Neurons travel up radial glial cells and so they can leave deep VZ and differentiate
* These cells are only seen in developing NS

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6
Q

Mantle Zone (MZ)

A

Neurons leave radial glial cells and accumulate superficially forming MZ
* Next wave will follow same process but jump off earlier and differentiate under previous layer

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7
Q

What happens to VZ as more neurons are generated?

A

It becomes thinner
* MZ thickens.

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8
Q

Cortical Layer 4

A

Receives Thalamic projections
* High density of stellates
* Sensory
* Project to 2-3

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9
Q

Cortical Layer 2-3

A

Intracortical connectivity between areas/layers, across Corpus Cal.
* Small pyramidal cells
* Project down to 5-6

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10
Q

Cortical Layer 5

A

Main output layer to distant subcortical centres
* Has biggest cells
* Long distance

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11
Q

Cortical Layer 6

A

Projections to Thalamus
* Relay sensory info
* Output

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12
Q

Cortical Layer 1

A

Mainly acellular
* Dendrites

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13
Q

Subventricular Zone (SVZ)

A

Remnant of early embryonic layers
* Lay dormant
* Small no. of stem cells in the adult remain?

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14
Q

Where do cells start to differentiate in corticogenesis?

A

In the primordial plexiform layer (PPL)

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15
Q

What occurs when the second wave of neurons hop off radial glial cells in corticogenesis?

A

They leave and split the initial layer of cells into a superficial (Marginal Z) and deep layer (SubP)
* This middle layer will the the cortical plate (CP)

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16
Q

How many layers come from the CP?

A

All except layer 1

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17
Q

What occurs to subsequent waves following formation of CP

A

Move up and differentiate superficially.
* MZ > Layer 1

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18
Q

Intermediate zone (IZ)

A

White matter forming below CP

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19
Q

Do inhibitory neurons travel up radial glial cells?

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A

No, they are generated subcortically and travel tangetially

20
Q

Excitatory Interneurons

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A
  • Glutamatergic
  • Travel up Radial Glial
  • 80%
21
Q

Inhibitory Interneurons

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A
  • GABAergic
  • Forerunner of basal ganglia
  • Less tightly controlled (complex and longer migration)
22
Q

Where do Wnts and BMPs come from?

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A

Caudal and Medial regions

23
Q

Where do fibroblast growth factors (FGFs) come from?

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A

Rostral regions

24
Q

Where do Epidermal growth factors (EGFs) come from?

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A

More Lateral regions

25
What effect does Wnts, BMPs, EGFs, FGFs have?
Act as ***morphogens*** and sets up *gradients* of **transcription** factors
26
What are growth cones?
*Tip* of **growing axon** * Have **processes** that sample enviro * **Decision** making
27
Filopodia
***Long, skinny*** processes on the growth cone
28
Lamellipodia
***Flat*** processes on the growth cone
29
Extracellular matrix adhesion
Growth cone must ***adhere*** to something for **cellular machinary** to work (e.g. ***cell surface***)
30
Fasciculation
Growth cone ***adhere*** to **axon** of another neuron that has already ***grown further*** down the pathway
31
Chemoattraction
**Soluble** molecule released from signalling centre. Sets up ***gradient*** to attract
32
Contact inhibition
**Surface** of cells ***push*** the growth cone away. **Discourage** adherence
33
Chemorepulsion
Molecule is ***inhibitory*** to growth of axon
34
First decision in the retinotectal pathway
**RGCs** growing on *superficial* surface of retina need to make a **90°** turn into ***optic nerve head*** > proper
35
Second decision in the retinotectal pathway
Occurs at ***optic chiasm***: * **Temporal** > stay ipsilateral * **Nasal** > cross over ***contralaterally***
36
What happens when a growth cone needs to make a decision?
1. It ***slows*** down 2. Becomes more **complex** 3. **Processes** are working
37
Axons in the optic chiasm
**Nasal**: ***crosses*** midline **Temporal**: ***turns*** before reaching midline (growth cone that is *close* to the middle line **collapses**)
38
Netrin and its receptors
**Soluble** * Receptors: **DCC** & **Unc5** * If **DCC + Unc5** present: ***REPULSION*** * **Only DDC**: ***ATTRACTION***
39
Slit
**Soluble** * Mostly ***REPULSIVE*** with **Robo**
40
Ephrins
Mostly ***REPULSIVE*** with **Eph**
41
Mapping of vision
*Pass* optic chiasm > ***Superior Collic***. * **Nasal** axons > **caudal** part of tectum * **Temporal** axons > **rostral** part of tectum
42
Why is mapping and decision making so important for binocular vision?
**Light** hits our eyes in ***straight lines*** at different points in the retina. Need a **spacially accurate** view
43
Membrane Stripe Assay
Take *cell membranes* from *rostral* and **caudal** * **Nasal**: didn't show a bias * **Temporal**: **ONLY** grow on the anterior/***rostral*** stripes. Something repelling in the caudal portion?
44
EphA receptors + ligands in the retinotectal pathway
* **Temporal** RGCs show high expression of ***EphA5*** (low nasally) * **Caudal Superior Collic**. show high amount of ***ephrin A5 ligand*** (none rostrally)
45
Refinement of projections
Early projections are ***exuberant*** Adult - **refined**
46
What happens when synapses aren’t effective at driving post-synaptic responses?
They get ***pruned away*** and those that are more **effective** branch and ***takeover***

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