Myelination 1 Flashcards
(31 cards)
Role of myelination?
Increases speed of AP conduction along an axon
How can AP speed be increased?
Larger axons, increased body temp, fatty insulation
Name of gaps between myelin?
Nodes of Ranvier
What is saltatory conduction?
AP can jump between NoR, increased speed of axonal transmission
Two primary mechanisms of myelination?
Oligodendroglia and schwann cells
Where are Schwann cells active?
PNS
Where are oligodendrocytes active?
CNS
How many axons can a schwann cells myelinate?
Single axon at a single point
How many axons can an oligodendrocyte myelinate?
Multiple axons in its vicinity
How are NoR locations determined?
Where the axons is myelinated
What is a myelin sheath composed of?
Many loops of a glial process
Where are schwann cells derived from?
Neural crest, and a small contribution from the ventral neural tube
Where are oligodendrocyte progenitors found?
ventricular zone of the neural tube
What is the oligodendrocyte precursor cell?
O2A cell
Use of markers of oligodendrocyte precursors in spinal cord?
Mapping migration
Markers of oligodendrocyte precursors in spinal cord
olig-2, sox10, PDGFRalpha
What causes oligodendrocytes to migrate in the neural tube?
SHH signalling–> triggers a phenotypic change
What happens to oligodendrocytes migration ability as they differentiate more?
Migration ability decreases
How do oligodendrocyte precursors know where to migrate to?
Follow radial glia Follow developing axon pathways
OPs require cell adhesion molecules for migration
Why do oligodendrocytes need an interaction with an axon?
If they dont receive an input from an axon they die via apoptosis as they wont receive growth factors
What happens if an oligodendrocyte precursor receives input from an axon?
It begins to differentiate,
What happens when a schwann cell reaches an axon?
It begins to myelinate it
Which myelinating cells are dependent on the axon for their whole life?
Oligodendrocytes
What are the two cells that develop from an immature schwann cell?
Myelinating schwann cell and non-myelinating schwann cell
