Regeneration in the nervous system

Question 1

What can be regenerated in the newt?

Answer 1

If you trim the newts limb it will regenerate in 70 days including the restoration of the bone, muscle and skin

Question 2

Tadpole tail regeneration is triggered by what?

Answer 2

BMPs

Question 3

The star fish will regenerate limbs if what nerve is still present?

Answer 3

The radial nerve

Question 4

What are the structures making the nerve (smallest to biggest)

Answer 4

Schwann cells
Endoneurium - surrounds several axons = fasicles of nerves
Perineurium - fasicles and blood vessels
Epineurium - outer layer

Question 5

What are the three basic classes of nerve injuries?

Answer 5

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

Question 6

Who improved Seddon’s nerve injury classification?

Answer 6

Sunderland

Question 7

What are Sunderland’s degrees of nerve damage?

Answer 7

1) Neuropaxia
2) Axonotmesis (has endoneurium)
3) Damage to the endonerium tube
4) Neurotmesis with epineurium
5) Neurotmesis without epineurium

Question 8

Where in the cell is damage more likely to cause cell death?

Answer 8

Close to the cell soma

Question 9

What is wallerian degeneration?

Answer 9

Section of nerve/axon degenerates very quickly (away from the cell soma), occurs by macrophages and takes place very quickly

Question 10

What happens to a denervated muscle?

Answer 10

Muscle atrophy occurs very quickly
Acetlycholine recepeptors change to more embryonic isoforms
Upregulation of muscle specific kinase

Question 11

What can help prevent muscle atrophy?

Answer 11

External electricasl input can help

Question 12

Describe nerve regeneration in the PNS

Answer 12

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

Question 13

What is a crush injury?

Answer 13

Where the basal lamina is disrupted but the ECM is intact

These nerves show better re-growth with accuracy

Question 14

What is a cut injury?

Answer 14

Where both the basal lamina and ECM is not intact

These nerves may not regrow accurately

Question 15

What are the properties of spinal cord nerve injuries?

Answer 15

Sprouting occurs followed by failed regeneration - this causes degeneration
Cysts and glial scars form
Recovery of connections is difficult

Question 16

What is the suggested reason that PNS nerves can regenerate but CNS nerves can not?

Answer 16

They nerves in the CNS have inhibitory myelin surrounding them
CNS nerves on PNS schwann cells can reconnect

Question 17

How can CNS regeneration be improved?

Answer 17

Autoimmunisation to myelin proteins

Question 18

Which myelin protein inhibits axon growth?

Answer 18

Nogo- a

Question 19

What are the three types of NOGO and where are they found?

Answer 19

a = oligodendrocytes and developing neurons
b = many cells
c = muscle

Question 20

Knockouts of nogo -a show what?

Answer 20

Improved regeneration in the CNS due to decreased inhibition

Question 21

What are the objections to the NOGO theory?

Answer 21

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

Question 22

Why could astrocytes be responsible for poor regeneration?

Answer 22

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

Question 23

What do astrocytes secrete to prevent regeneration?

Answer 23

Inhibitory condroitin sulphate proteoglycan which prevent axons to grow through as they are big ECM proteins

Question 24

What are spinal cord bridges?

Answer 24

Biological (sural) and artificial bridges may be used to connect nerves together to allow them to grow

Question 25

Name four ways to repair nerves

Answer 25

1) Transplant foetal cells
2) Transplant hESC - derived progenitors
3) Transplant umbilical cells
4) Transplant autologous nervous system/ other cells

Question 26

How can it be seen where new DNA is being made?q

Answer 26

Inject tinitin

Question 27

What are the two areas in the adult brain where neurogenesis occurs?

Answer 27

SVZ - connects with the olfactory bulb

Dentate gyrus in the hippocampus

Question 28

What are olfactory ensheathing cells?

Answer 28

Supporting cells that have a good ability to support regneration
These have been used to help complete gaps in the spinal cord