L22 - Myelin

Question 1

Saltatory conduction

Answer 1

Saltatory conduction (from the Latin saltare, to hop or leap) is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.

Question 2

Myelin and learning?

Answer 2

Myelin is dynamic and changes with learning- interpreted as amount of myelin increase, increasing conduction velocity, neural synchronization that enables skill acquisition

E.g. When no new myelin can be formed, the mice couldn’t learn anything new

Question 3

Myelin and neuronal survival?

Answer 3

Oligodendrocyte dysfunction leads to axonal degeneration as axons have high metabolic demands and axons require the specialised transport of lactate from oligodendrocytes

Question 4

Leukodystrophies

Answer 4

Myelin is not produced properly (often inherited, autosomal recessive)

Question 5

MS

Answer 5

Auto-immune inflammatory disorder where myelin is attacked by external substances

• Cause unknown
• Disease course is highly variable

Question 6

Is abnormal myelination associated with neurological disorders and mental illness?

Answer 6

Is abnormal myelination associated with neurological disorders and mental illness?

Question 7

Peak onset?

Answer 7

25-30 year old females> males

Question 8

4 x more likely to get MS if you live in Tasmania rather than Hobart - why?

Answer 8

Sunlight suppresses immune system and influences myelin

*The closer you are to equator, the lower you have MS

Question 9

Inverse relationship between infections and immune disorders - less infections but more immune disorders. What is the hypothesis that explains this?

Answer 9

Hygiene hypothesis - lack of early childhood exposure to infectious agents increases susceptibility to allergic diseases by suppressing the natural development of the immune system

Question 10

Genetics and MS

Answer 10

Monozygotic twins have 30% risk of MS development

Question 11

BDNF and myelin

Answer 11

BDNF promotes oligodendrocytes myelination by ERK 1/2 (MAP kinases transcriptional activator that phosphorylate trasnscription factors) and 5 signalling pathways

Question 12

BDNF is 30 kilodaltons, way too big to be effective drug - what do we use instead?

Answer 12

TDP6 - BDNF mimetic that is 1.5 kilodaltons

Question 13

TAM signalling modulates CNS demyelination during development and repair

Answer 13

TAM signalling modulates CNS demyelination during development and repair

Question 14

Are oligodendrocytes present in lesions?

Answer 14

Yes - they are there but fail to remyelinate