Peripheral Nerve Injury Flashcards
Axonal response to injury
Wallerian degeneration
Wallerian degeneration aka
anterograde degeneration
…. is the process that occurs when an axon/nerve fiber is cut, severely tractioned (to the point of separation), or crushed. It can also occur when axons sustain severe and prolonged compression
Wallerian degeneration
Wallerian degeneration occurs in stages:
- Degeneration
- Clearance
- Regeneration
- Growth and re-myelination of new axons
T/F Degeneration is when injury causes the Proximal part of the axon to become separated from its cell body.
Fasle
Distal
T/F In Degeneration, the injured axon(s) that is no longer connected to its cell body degenerates proximally from the injury site all of the way along its pathway
False Distally
It also degenerates for a short distance proximally from the injury site to the nearest node of _________ .
Ranvier
Axonal degeneration is followed by degradation of the myelin sheath and neurolemma: infiltration by macrophages, mast cells and Schwann cells clear fragmented axonal material and debris from the injury site and along the pathway of the axon.
- Clearance
During Clearance, the axon, myelin sheath and neurolemma of each injured axon have now _________ from the site of the injury along the pathway of the nerve.
Degenerated
During Clearance, all that remains distal to the injury site is the nerve stroma, i.e. the epineurium, perineurium and __________ sheath. Exceptions include crush injuries and any other injuries that destroy ______ nerve stroma)
Endoneurial
Distal
During Clearance, The endoneurial sheath distal to the injury remains as a hollow tube and is ________ for regeneration
ESSENTIAL
During Regeneration, these cells rapidly reproduce and migrate from nearby neurons and via the blood
stream towards the injured nerve?
Schwann Cells
During Regeneration, the______ ______ shifts its function from synaptic transmission to cellular ______. Axoplasmic material, nutrients and building blocks are moved from the cell body along the ______ intact part of the axon towards the injury site.
cell body
repair
proximal
During Regeneration, _________ sprouting: the proximal end of the axon sends out neuronal sprouts which advance towards the intact _________ tubes distal to the injury site
Neuronal
Endoneurial
During Regeneration, the axonal sprouts begin bridging the gap between the _______ and _______ connective tissue segments while the cell body continues to send building blocks along the ______ towards the regenerating axon.
Proximal and Distal
Axon
______ _______ is the initial healing phase lasts on average 10 – 12 days
Gap Repair
Gap repair lasts how long on average?
10-12 days
Gap repairs includes how many steps? Name them?
Name the other aspects within gap repair?
3
Initial injury
Degeneration
Clearance
Cell body production of new axoplasmic material
Neuronal sprouting from proximal stump of injured axon towards the distal endoneurial tubes.
what is the initial healing time?
is the time it takes for the degenerated axon to bridge the gap between the proximal and distal segments of the injured nerve and reach the distal endoneurial tubes.
During Growth and re-myelination of new axons, If the neuronal sprout reaches the distal endoneurial tube, it grows into it and advances along the _______ _________, gradually reaching and re-innervating its target tissues.
nerve pathway
During Growth and re-myelination of new axons, as the newly constructed axon moves along the _______ tube, Schwann cells ____-________ the axon.
Endoneurial
Re- myelinate
In summary, the only way a particular axon can become functional again is through growth of the _________ part of the axon into the correct _________ tube and along its original route
Proximal
Endoneurial
T/F Regeneration on average is said to occur at a rate of 1 mm per day
True
