Regeneration in the nervous system Flashcards
(28 cards)
What can be regenerated in the newt?
If you trim the newts limb it will regenerate in 70 days including the restoration of the bone, muscle and skin
Tadpole tail regeneration is triggered by what?
BMPs
The star fish will regenerate limbs if what nerve is still present?
The radial nerve
What are the structures making the nerve (smallest to biggest)
Schwann cells
Endoneurium - surrounds several axons = fasicles of nerves
Perineurium - fasicles and blood vessels
Epineurium - outer layer
What are the three basic classes of nerve injuries?
Neurapaxia- mild, occurs due to compression eg there is no conduction but the nerve is not physically breached
Axonotmesis - preservation of the nerve despite damage, no conduction
Neurotmesis - most severe, whole nerve is divided
Who improved Seddon’s nerve injury classification?
Sunderland
What are Sunderland’s degrees of nerve damage?
1) Neuropaxia
2) Axonotmesis (has endoneurium)
3) Damage to the endonerium tube
4) Neurotmesis with epineurium
5) Neurotmesis without epineurium
Where in the cell is damage more likely to cause cell death?
Close to the cell soma
What is wallerian degeneration?
Section of nerve/axon degenerates very quickly (away from the cell soma), occurs by macrophages and takes place very quickly
What happens to a denervated muscle?
Muscle atrophy occurs very quickly
Acetlycholine recepeptors change to more embryonic isoforms
Upregulation of muscle specific kinase
What can help prevent muscle atrophy?
External electricasl input can help
Describe nerve regeneration in the PNS
Regeneration involves:
mitosis of schwann cells - they cover the area to supply growth factors
Formation of bands of buger - these are rows of schwann cells which guide the axons
Wallerian degeneration must have occured very quickly to remove debrin
What is a crush injury?
Where the basal lamina is disrupted but the ECM is intact
These nerves show better re-growth with accuracy
What is a cut injury?
Where both the basal lamina and ECM is not intact
These nerves may not regrow accurately
What are the properties of spinal cord nerve injuries?
Sprouting occurs followed by failed regeneration - this causes degeneration
Cysts and glial scars form
Recovery of connections is difficult
What is the suggested reason that PNS nerves can regenerate but CNS nerves can not?
They nerves in the CNS have inhibitory myelin surrounding them
CNS nerves on PNS schwann cells can reconnect
How can CNS regeneration be improved?
Autoimmunisation to myelin proteins
Which myelin protein inhibits axon growth?
Nogo- a
What are the three types of NOGO and where are they found?
a = oligodendrocytes and developing neurons b = many cells c = muscle
Knockouts of nogo -a show what?
Improved regeneration in the CNS due to decreased inhibition
What are the objections to the NOGO theory?
There is no correlation between nogo/receptor level and regenerative capacity
Transplanted hippocampal neurons grow axons in myelin
Much myelin is removed by macrophages after CNS degeneration anyway
Why could astrocytes be responsible for poor regeneration?
They try to limit the level of injury by creating a scar made up of inhibitory tissue
These scars are found in all parts of the CNS but not the PNS
What do astrocytes secrete to prevent regeneration?
Inhibitory condroitin sulphate proteoglycan which prevent axons to grow through as they are big ECM proteins
What are spinal cord bridges?
Biological (sural) and artificial bridges may be used to connect nerves together to allow them to grow
