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Neuro U3 > Axonal growth, synaptogenesis and tropism Lec 3 > Flashcards

Axonal growth, synaptogenesis and tropism Lec 3 Flashcards

1
Q

Polarization

A

First step in neuronal identity
one process becomes axon
-with growth cone

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2
Q

Axonal growth cone structure and fxn

A

Explores EC env
determines direction of growth
Guides extension of axon

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3
Q

Lamellapodium

A

actin filaments and mircrotubules

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4
Q

Filopodia

A

Extends out of lamellapodium
actin filaments
form and disappear rapidly

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5
Q

Globular actin (G-actin)

A

part of growth cone cytoskeleton
can be incorporated into F-actin
Respond to environmental cues

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6
Q

Growth cone turning

A 
Binding of F-actin
-recruits proteins
attractive cues
-assembly increased
retrograde slowed
turns to attractive cue
(repulsion opposite)
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7
Q

Microtubules

A

Stability and strength

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8
Q

Discrete regions of cytoskeleton

A

F-actin- lamellipodium
Tyrosinated microtubules- lamellipodium
acetylated microtubules- axons only

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9
Q

Guidance molecules- nondiffusible

A

contact attraction

contact repulsion

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10
Q

Guidance molecules- diffusible

A

Chemoattraction

chemorepulsion

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11
Q

Attractive interactions

A

Actin polymerization

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12
Q

Repellent interactions

A

actin depolymerization

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13
Q

PNS molecules

A 
Laminins
collagens
fibronectin
- bind integrins
- leads to axon growth and elongation
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14
Q

CNS molecules

A

Hyaluronan
proteoglycans
glycoproteins
- repulsive to axonal growth and inhibit cell movement

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15
Q

Cell adhesion molecules CAMs

A

Non-diffusible
Ligands and receptors on surface of axons/growth cones
Ca independent
Induces interation with cytoplasmic kinases in growth cone
attraction

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16
Q

Cadherins

A

Non-diffusible
Ligands and receptors on surface of axons/growth cones
Ca dependent
triggers intercellular signaling pathways that lead to actin binding and organization
Attraction

17
Q

Semaphorins

A

Non-diffusible
Cell surface
Repellent
Growth cone collapse and inhibition of axon extension

18
Q

Ephrins

A 
Non-diffusible
cell surface like CAMS
Ephrin A- GPI linked
Ephrin B- single pass transmembrane protein
Repellent- collapse growth cones
19
Q

Netrins

A

Diffusible
Midline of embryo
Attractive and repellent- depends on receptor
DCC= attractive
UNC5= repellent
Key role in commissural axonal crossing in developing spinal cord

20
Q

Slits (robo)

A

Diffusible proteins

repellent

21
Q

Netrins and slits in commissural axons

A

DCC expressed- attracts to midline
- produces high level of netrin
Slits (robo) upregulated
- inhibits DCC signaling

22
Q

Synaptogenesis NMJ

A 
Motor axon- myotube
differentiation occurs by argin
- produces MuSK- clustering of AchR and rapsyn
ECM formed
-make basal lamina
-stabilizes synaptic structure
23
Q

Synaptic specificity

A

T1-eye
T4-ear
both use same sympathetic pathway
differential innervation occurs at level of synapse formation

24
Q

CNS synaptogenesis

A

Neuroxin and Neuroligin

25
Q

Neuroxin

A

Presynaptic

  • cytoskeletal elements
  • Synaptic vesicles
  • Ca channels
26
Q

Neuroligin

A

Postsynaptic

-NT receptors

27
Q

PNS synaptogenesis

A

Neurons dependent on targets for survival and differentiation
Neurotrophic factors
-Skeletal muscle fibers and some parasym neurons innervated by multiple neurons- synaptic input are gradually eliminated until only one remains

28
Q

Neurotrophic factors

A

Neurons compete for limited supply

29
Q

Neurotrophin family

A

Nerve growth factors
-acts on specific popns of peripheral neurons
different neurons respond differently to NGF

30
Q

Neurotrophin family fxn

A

Survival
Formation/maintenance
synapses formation

31
Q

Neurotrophin receptors

A

Trk

P75

32
Q

Trk receptor

A

High affinity for processed (cleaved) neurotrophins

33
Q

P75 receptor

A

High affinity for unprocessed (uncleaved) neurotrophins

-can be activated by all neurotrophins

34
Q

Neurotrophin signaling

A

Specific cascade activated determine cellular response

35
Q

Neurotrophin signaling interactions depend on and determine what

A

Depend on

  • neurotrophins secreted by target cells
  • neurotrophin receptors on neuron
  • intracellular signaling cascades present in neuron

Determine

  • number of neurons
  • shape
  • pattern of connections

Neuro U3 (17 decks)

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