1.13 Regeneration of the CNS Flashcards
What is Neuropraxia?
Minimal damage to the neurone and the axon remains intact. However conduction ceases due to demyelination and local ischemia. Recovery within a few days or weeks
What is axonotemesis?
An axon is damaged to the extent of the distal portion degenerates, usually due to traction or compression. Slow regeneration occurs because the investing sheaths have remained
What is neurotmesis?
Distal and proximal parts are completely separated, proximal can only regenerate if the investing sheaths are repaired
Describe the process of neurone degeneration….
- if axon is cut, transmission completely ceases, then motor terminal degenerates
- Wallerian degeneration then occurs
- Muscles undergoes atrophy
- Schwann cells withdraw - leave debris
- Macrophages phagocytose distal axon
- Chromatolysis occurs; Nucleus is displaced, Nissls (RER) is dispersed and gene expression and electrical responsiveness changes
- Synaptic contacts removed
Describe the process of Wallerian Degeneration…
Unravelling of the sheath outside of the axon along with neurofilament clumping inside. Between 1 week and 2 months after damage, the axon swells and bears down into small beading segments.
It is said to be an active process - similar to apoptosis
Describe the process of motor axon regeneration…
- Motor neurone synthesise proteins needed for regeneration such as neurofilaments, growth cone proteins and microtubules.
- axon will sprout - if lucky it finds a shwann cell to guide its growth,
- Motor axon contants muscles - retrograde signals to increase gene expression in order to allow it to function again
PS protein GAP 43 is up-regulated.
What prevents regeneration in the CNS?
Myelin sheath in the CNS contains proteins that inhibit regeneration and growth.
Also astrocytes form a scar.
Microglia slowly clear any debris.
Dont up regulate GAP 43
In the future, how can the CNS inhibition of regeneration be treated?
Inject with antibodies against myelin inhibitory proteins, thus promoting sprouting and regeneration of axons.
What are the barriers to repair of a spinal cord injury?
- Loss of Cells
- Damage to axons, through inflammation, atrophy and demyelination
- Inhibitory environment for regeneration
- Reduced capacity for growth of adult neurones
How could the barrier of “loss of cells” be overcome in the future?
Transplant fetal tissue
Stem cells: endogenous, embryonic or bone marrow derived
Transplant glia to remyelinate
How could the barrier of “Damage to axons” be overcome in the future?
Enhance compensatory sprouting of axons
Give neutrophins to stimulate growth
Where are endogenous stem cells found and what is there therapeutic effect?
Subventricular zone and dentate gyrus.
They can be used to boost activity with growth factors.
