Schwann Cells

Question 1

Difference between Schwann cells and Oligodendrocytes

Answer 1

Oligodendrocytes myelinate multiple axons while Schwann cells are in 1:1 ratio w/ axons

NB: CNS cells need more myelinatiom

Question 2

Components of Nodes of Ranvier

Answer 2

Sodium channel
Caspr (Contactin associated protein)
Potassium channel

Question 3

Resting membrane potential voltage

Answer 3

-70mv intracellularly

Question 4

Types of nerve fibres w/ description of myelination

Answer 4

A-fibre: myelinated (v fast conduction)
B-fibre: myelinated (fast conduction-slower than A)
C-fibre: not myelinated (relatively slow conduction)

Question 5

Describe relationship between Schwann cells and myelinated fibres vs unmyelinated fibres

Answer 5

Myelinated fibres are axons surrounded by Schwann cells

Unmyelinated fibres are also axons surrounded Schwann cells but there is no myelination. This is called a Remak bundle

Question 6

Where do Schwann cells originate?

Answer 6

Neural Crest

Question 7

Describe Schwann Cell lineage

Answer 7

Neural crest cell -> Schwann cell precursor -> immature Schwann cell

-> promyelin Schwann cell -> myelin Schwann cell
OR
-(radial sorting)> nonmyelin (Remak) Schwann cell

NB: myelin and nonmyelin can regenerate into each other type via the intermediate repair (Bungner) Schwann cell

Question 8

______ is essential for both myelination and Remak bundles formation

Answer 8

Neuregulin-1 Type III

secreted by neurons and essential for survival after E.18

Question 9

Receptor for Neuregulin-1

Answer 9

ErbB3 / ErbB2

Question 10

What determines how many axons a Schwann cell will segregate?

Answer 10

Neuregulin-1; Overexpression of NRG1 causes previously unmyelinated axons to become myelinated (e.g. sympathetic fibres)

NB: Axon diameter: Myelin thickness relationship is determined by the amount of axonal NRG1 type III

Question 11

Low levels of NRG1 -> ___

High levels of NRG1 -> ___

Answer 11

Low levels of NRG1 -> Remak bundle
High levels of NRG1 -> myelination

A fibre: Myelinated
B fibre: Myelinated
C fibre: Remak bundles

Question 12

Transcription factor essential for myelinating Schwann cells?

Answer 12

Krox-20

NB: NOT FOR REMAK BUNDLE PATHWAY

Question 13

Where are is Nav1.8 located?

Answer 13

Located at discrete points along neurites and co-localises w/ lipid rafts

Question 14

Sodium channel for unmyelinated fibre;___

Sodium channel for myelinated fibre: ___

Answer 14

Sodium channel for unmyelinated fibre: Nav1.8

Sodium channel for myelinated fibre: Nav1,6

Question 15

What are lipid rafts?

Answer 15

Microdomain on a membrane- acts as a platform where proteins are sorted and functionally localised

Question 16

What is the specific function of lipid rafts on axons?

Answer 16

Aid the clustering of Nav sodium channels

NB: if lipid raft knockout, sodium channels will disperse and there’s no response to the stimulus