05 | Axonal Growth Flashcards
Components of GC
1) Lamellipodia
2) Filopodia
Which enzyme is responsible for pruning of synapses?
caspases
What happens when an PNS neuron is damaged?
- Distal myelin sheath degenerates
- Schwann cells + macrophages clean up debris
- Cell body swells
- Nucleus swells and moves off-center
Retrograde signalling of damaged neuron
- tell presynaptic axon to retract
- tell undamaged nearby neurons to make more synapses to compensate
Effect of denervation on postsynaptic cell
- muscle fibrillations
- TTX-resistant channels
- atrophy (long-term)
Effect of denervation on presynaptic cell
- synapse weakened
- retraction of axons
Factors for Schwann cell proliferation
- LIF
- Reg-2
- ApoE
Evidence for glial cell inhibition
- Axons in CNS don’t regenerate well, but axons in periphery do (even if cell body is in CNS)
- Axons will regenerate toward spinal cord, but stop when they hit astrocytes or glial scars
Nogo
protein on surface of oligodendrocytes; induce collapse of GCs, inhibit neurite growth
Limiting factors for regeneration in CNS
- injured neurons die
- no NTF
- molecules in extracellular matrix create hostile environment
- glial scars
- lack of growth-promoting proteins
- injury associated signals
Where are Schwann cell bridges found?
Olfactory system
Schwann cell bridges are sometimes useful for…? (specific example)
reconnection of retina and superior colliculus
List the steps of long range chemo-guidance of an interneuron across the spinal cord
- [Long-range attraction] floor plate secretes Netrin-1, which attracts with DCC
- [Short-range attraction] floor plate secretes NrCAM, which attracts TAG-1
- [Short-range repulsion] floor plate tells GC to stop producing TAG-1, and produce Robo instead. Floor plate secretes Slit, which repels Robo.
What are the reasons for pruning after synaptogenesis?
- Ensure innervation by correct axons
- Correct mistakes
- Pathway establishment
Receptor for NGF
TrkA-R
