nerve regeneration and repair

Question 1

what can cause damage to nervous system occur:

Answer 1

• acute injury: tbi, spinal cord injury, strokes, limb damage
• degenerative diseases with loss of neurons; alzheimer’s parkinson’s, ALS
• loss of myelin: MS

Question 2

What part of the brain is really deteriorated in alzheimer’s patients?

Answer 2

grey matter esp. in the temporal lobe in the area of the hippocampus

Question 3

what is tau?

Answer 3

a protein associated with neuronal damage seen in alzheimer’s

Question 4

what accompanies brain tissue damage in tbi of football players and soldiers?

Answer 4

changes in mood, depression, and cognitive problems

Question 5

what is required for nerve regeneration>

Answer 5

• survival of the nerve cell body
• clearance of the damaged distal axon, myelin breakdown products, and other tissue debris
• an environment that stimulates new axonal
• guidance cues for the axon to find its original cellular target

Question 6

what is the critical step for nerve repair in the CNS and PNS?

Answer 6

wallerian degereneratlon

Question 7

what is perineurium composed of?

Answer 7

ECM proteins that can promote axon elongation after injury

Question 8

if any nerve regrowth does occur how long does it take?

Answer 8

it can take weeks ,months, a year

Question 9

what is wallerian degeneration?

Answer 9

removal of damaged axons, damaged tissue and myelin debris

Question 10

what is the role of schwann cells in the regeneration of axons?

Answer 10

schwann cells release trophic agents to align and guide growing axon.

Question 11

when does wallerian degeneration start?

Answer 11

it is underway within 1 week of injury ( quickly w/ in 5-30 minutes of the injury)

Question 12

a nerve cut is harder to repair than a nerve __________

Answer 12

a nerve crush ( compression)

Question 13

in a nerve crush what happens to the axons?

Answer 13

some axons remain , density just decreases. the surviving ones can make new connections.

but you must get rid of the debris before axons can regrow in both crush and nerve cut

Question 14

what is the key to successful regeneration in the periphery?

Answer 14

schwann cells : they normally myelinate peripheral nerve, but in this case they will differentiate and proliferate secrete ECM proteins that stimulate axonal sprouting and elongation

they area also a source of neurotrophins

Question 15

what is the role of the bands of bungner?

Answer 15

they are the remaining tubes of ECM that act as guidance cues

Question 16

how do PNS nerves that regenerate know where to reconnect with muscle?

Answer 16

the Ach receptors remain where axons terminates and therefore provide guidance cues for regenerating axon to find where previous axons were.

Question 17

the reinnervation of muscles following peripheral motor nerve damage is ________

Answer 17

precise

Question 18

compared to the PNS the repair in the CNS is ?

Answer 18

not very effective

Question 19

most studies of CNS repair are centered around trying to restore _______ ________ after ______ ______ _______

Answer 19

restore motor fnc after spinal cord injury

Question 20

even though many there is often prolonged survival of neuronal cell body in the CNS why is it that effective regeneration is not seen?

Answer 20

because the other 3 requirements are exhibited ( clearance of damaged distal axon, environ which stimulates axonal regrowth, guidance cues for the axon to find it’s original cell target)

Question 21

what is the reason why wallerian degeneratioin is inefficient in the CNS?

Answer 21

because when myelin breaks down some of the products are inhibitory to axonal regeneration: a GLIAL SCAR is formed in an attempt to limit tissue damage in the CNS this forms a physical barrier to repair .

Question 22

what does a glial scar produce?

Answer 22

chondrotin sulfate proteoglycans which forms a physical barrier to regeneration and remyelination

Question 23

in what disease processes are chondrotin sulfate proteoglycans seen?

Answer 23

multiple sclerosis, Alzheimer’s etc.

Question 24

how does a graft help with nerve regeneration?

Answer 24

provides a source of growth factors to stimulate axonal regeneration and neuronal survival as well as a permissive on which axons can easily grow.

Question 25

how does chondrotinase treatment help nerve regeneration?

Answer 25

it removes the sugars from the chondrotin sulfate proteoglycans essentially removing the barrier which the sugar cause , this creating a permissive environment where axons can regenerate and oligodentrdrocyte progenitor cells can move in and remyelinate axons.

Question 26

where are the only neurons that can be replaced if a neuron is lost?

Answer 26

the adult brain olfactory bulb and the hippocampus

Question 27

what is a major problem for stem cells within the CNS?

Answer 27

guidance cues and pathways ( i.e. lack thereof)

Question 28

neural stem cells are?

Answer 28

committed but multipotenet

Question 29

what type of stem cells are pluripotent and what issues do these cells pose?

Answer 29

embryonic stem cells ( sometimes they don’t differentiate, and they are tumorgenic)

Question 30

adult stem cells are

Answer 30

multipotent

Question 31

to successfully restore function to a stem cell what must be achieved?

Answer 31

• cell must differentiate into the appropriate kind of neuron
• make connections w/ the appropriate target cells
• form working synapses

Question 32

how does differentiation of stem cells into oligodentrocytes help regeneration?

Answer 32

it enhances the remyelination of spared axons near the lesion which enhances the ability of axons to transmit nerve impulses

Question 33

what is the best option for repair?

Answer 33

combination of therapies to enhance tissue recovery and restore fnc

Question 34

how can physical therapy help with regeneration/repair?

Answer 34

can stimulate the endogenous production of neurotrophins that promote repair