Neuroregeneration Lec24

Question 1

Nerves can sometimes regenerate in the ___

Answer 1

PNS

Question 2

Nerves can almost never regenerate in the ___

Answer 2

CNS

Question 3

Effective nerve regeneration requires: (4)

Answer 3

1. survival of the nerve cell body (damage to axon only) 2. clearance of the damaged distal axon, myelin breakdown products, and other debris 3. a supportive environment that stimulates new axonal regrowth (limited inflammation) 4. guidance cues for the axon to find its original cellular target

Question 4

after injury CNS Wallerian degeneration is ___ and ___

Answer 4

slow and incomplete

Question 5

what is one reason why the CNS is a hostile environment for tissue regeneration? *

Answer 5

1. oligodendrocytes don’t help clean up debris so myelin persists in the CNS
2. CNS neurons result in a glial scar (purpose was to limit tissue damage – but now serve as a barrier)

Question 6

in PNS injury Denervated myelinating Schwann cells release their myelin and ___

Answer 6

proliferate, produce trophic factors, and phagocytose debris (~24 hours)

Question 7

After a nerve injury in the CNS and PNS, Wallerian degeneration occurs where the axon that is cut off is ___ and ____

Answer 7

degenerated and its myelin sheath degraded

Question 8

After nerve injury ___ and ___ are recruited work to clear away the debris.

Answer 8

schwann cells and macrophages

Question 9

after pns injury The macrophages produce factors that facilitate ___ and ___

Answer 9

Schwann cell migration & axon regeneration

Question 10

Injured axons form a growth cone and regenerate along the ___ formed by Schwann cells

Answer 10

bands of Bungner

Question 11

bands of Bungner guide the___ to their targets

Answer 11

growth cones

Question 12

Schwann cells that are chronically denervated for a few months are less supportive of regrowth and more likely to ____

Answer 12

apoptose

Question 13

If the axon can traverse the injury site, it may reconnect successfully. this typically takses

Answer 13

months to years

Question 14

compared to the original, the regenerated axon will have

Answer 14

thinner myelin and shorter nodal length

Question 15

why are come compression injuries easier to repair?

Answer 15

some axons may be spared - easier to repair.

Question 16

____ of muscles following peripheral motor nerve damage is precise - almost exactly the same as before injury

Answer 16

Reinnervation

Question 17

what does the CNS lack that may it ineffective at repair? (3)

Answer 17

1. clearence of debris
2. a supportive environment
3. guidance cues

Question 18

Wallerian Degeneration:
- acute axon degeneration is mediated by __ and ___

Answer 18

Ca influx and activation of calpain

Question 19

For___ hours after injury, the distal (disconnected) axon remains stable.

Answer 19

24-48

Question 20

Full fragmentation and breakdown of the distal axon occurs ~___ hours after injury,

Answer 20

72

Question 21

after full fragmentation and breakdown of the distal axon, ___ occurs

Answer 21

increased glial support (astrocytes and macrophages) to clear debris

Question 22

in PNS, Schwann cells shed myelin and ___.

Answer 22

proliferate

Question 23

in CNS, oligodendrocytes shed myelin and ____.

Answer 23

don’t usually proliferate

Question 24

Main culprit of the glial scar =

Answer 24

CSPG, chondroitin sulfate proteoglycans

Question 25

CSPG, chondroitin sulfate proteoglycans are produced by

Answer 25

astrocytes in response to injury, inflammation, or disease

Question 26

what are 6 Strategies to promote repair of the damaged nervous system:

Answer 26

1. biomaterials or peripheral nerve grafts
2. growth factors
3. agents to change local environement
4. cell replacement therapy to replace neurons or olgiodendrocytes
5. physical therapy

Question 27

how can Chondroitinase ABC help change local environements?

Answer 27

its an enzyme that can remove sugar side chains from

inhibitory proteoglycans of the glial scar

Question 28

Biomaterials or Peripheral Nerve Grafts could be used to provide a ____

Answer 28

a growth-promoting substrate

Question 29

Growth factors could be used to promote___ and ___

Answer 29

neuronal survival and axonal sprouting

Question 30

The perineurium is composed of extracellular matrix proteins that can promote ____

Answer 30

axon elongation after injury.

Question 31

The key to successful regeneration in the periphery is the ____

Answer 31

Schwann cell.

Question 32

regneerating axons can reconnect with target tissues because of guidance cues provided by ___ and ____

Answer 32

bunger and ach receoptors

Question 33

why is the concept important that “if the neuron is lost it cant be replaced”

Answer 33

without the neuron, you cannot get repair (need surviving cell body)

Question 34

what are some stem cell soruces?

Answer 34

Question 35

in addition to replacing cells that were lost, what could stem cells also be useful for?

Answer 35

Differentiation of stem cells to oligodendrocyte progenitor cells prior to transplantation enhances the remyelination of spared axons near the lesion

Question 36

physcial therapy can stimulate the endongeous poduction of ___ that promote repair

Answer 36

neutrophins