Section D: nerve injury and regeneration

Question 1

In axonal injuries, does an axon distal to the injury survive?

Answer 1

No, it dies after around 2-3 days. Whereas axons proximal to the injury survive.

Question 2

What are the types of glia and myelinating cells in the PNS vs CNS?

Answer 2

In the PNS, there are Schwann cells and Remak cells, whereas in the CNS there are astrocytes and oligodendrocytes.

Question 3

What does axon regeneration depend on? Link these back to CNS/PNS differences.

Answer 3

1) Intrinsic capacity of the neurone to build a new axon

2) The growth permissiveness of the axonal environment.

Question 4

Describe the gorwth cone, naming key parts.

Answer 4

Fast moving, contains microtubules and actin (Dense, complicated network).
Lamella podia (palm) and fila podia (fingers) that extend  the axon.

Question 5

When does a neurone stop growing?

Answer 5

Once it reaches the transmitting mode (i.e. when the growth cone transforms into an axon terminal - and a synapse is created).

Question 6

Name some neurone-types that have parts in both the CNS and PNS.

Answer 6

Motor neurones

DRG

Question 7

What happens if the motor neurone is cut? Does it reform?

Answer 7

YEs it does.

Question 8

Does DRG reform?

Answer 8

No.

Question 9

What does regeneration of the neurone depend on?

Answer 9

Location of the injury site. Success/failure of regeneration depends on environment.

Question 10

Describe an experiment showing how nerves can regenerate in the PNS.

Answer 10

Peripheral nerve implant - change of environment enables regeneration.

Question 11

What signals in the environment may cause neurones to regenerate (or not)?

Answer 11

Signals that promote or inhibit growth cone formation.

Control growth cone behaviour and axon growth.

Question 12

What does neuronal survival depend on?

Answer 12

Blood borne nutrients, specific survival factors (growth factors - e.g NGF) that block apoptosis.

Question 13

What does NGF do?

Answer 13

Nerve growth factor promotes axon growth and survival.

Question 14

Signals that promote axon growth?

Answer 14

Soluble (secreted) trophic factors - e.g. NGF, BDNF, GDNF.

Substrate bound factors - adhesion molecules inc. N-cam.

Question 15

Signals that inhibit axonal growth?

Answer 15

CNS and PNS myelin - MAG, Omg

Oligodendrocytes-associated - proteoglycans, tenascin, semaphorins, ephrinB2, slit