Regeneration in the NS Flashcards
(40 cards)
Why is regeneration in the NS important?
Large number of traumatic injuries in peripheral nerves annually
What are some causes of peripheral nerve damage?
- Spinal cord injury
- Stroke
- Degenerative diseases
- Road accidents
What is the regenerative capacity of lower animals (reptiles, amphibians, fish)?
Huge
How is xenopus tadpole tail regeneration triggered?
By BMPs
What is the ‘critical period’ of regeneration in the tadpole?
Time after this, there is a loss of BMP expression and the trail cannot regenerate
In lower animals, what is regeneration dependant on?
What are exceptions to this?
Nerves
Worms - if cut in half, both ends grow back
What is a blastema?
What is in close proximity to it? What does this allow?
Pluripotent stem cells in a salamander
In close proximity to nerves - where Schwann cells migrate in from and allow regrowth
In a nerve, what do the insulating layers impact on?
The damage the nerve can get and the ability of the nerve to repair itself
Who classified nerve injuries?
Seddon
What is Neuropraxia?
Damage to some of the insulating layers of the nerve - produced by compression or stretching
What does neuropraxia affect?
Conduction of the nerve (because of damage to the insulating layers)
What is axonotmesis?
Division of the nerve but the connective tissue remains intact
Nerve is resected
What is neuromesis?
Division through the entire nerve (through insulating layers and through the axon)
How was Seddons classification of nerves expanded?
At the level of axontemeis and neuromesis, can have different stages of conduction - some preservation or complete loss
What happens if the injury happens close to the cell body? (In the PNS)
Get cell death
What happens if the injury is not close to the cell body?
In the PNS
Re-organisation and re-expression of immature features (tubulin), depending upon the level of damage
What is Wallerian degeneration?
In the PNS:
When the nerve is damaged, the distal part of it starts to degrade as macrophages invade the area and break up the remnants of the destroyed cells and myelin to clean the area
What happens to muscle when the nerve innervating it is damaged? (PNS)
- Muscle atrophy
- AChR reversal to embryonic (de-differentiation)
- MUSK receptor increase
In denervated muscle, what can external electrical input help? (PNS)
Prevent atrophy and degeneration
How is the distal part of the nerve regenerated, if the connective tissue remains intact?
(PNS)
- Mitosis of Schwann cells, which supply growth factors
- Schwann cells rearrange themselves to produce BANDS OF BUNGNER (rows)
- This provides a scaffold for new axon fibres through the new connective tissue
What is sprouting?
When does it occur?
Compensation of loss of innervation to a muscle by an adjacent nerve innervating it instead
Occurs when peripheral nerves are damaged
What injury to the nerves have the biggest impact and why?
How can this be artificially compensated?
Injuries when the nerve is cut
As this disrupts the basal lamina and extracellular matrix
Schwann cells cannot grow
Artificially compensated by joining the 2 stumps of the neuron together
OR
By making a scaffold to breach the 2 sides
What occurs in the spinal cord after axon injury?
- Inefficient sprouting
- Followed by failed regeneration and degeneration
- Cysts and glial scar formation
- Poor recovery of connections
Why is regeneration in the spinal cord poor?
Inhibitory myelin and incorrect glia
