Nerve - myelination Flashcards
What is myelin?
A substance that wraps around a lot of axons in the NS to provide insulation and in turn, help with conduction. It also helps with the repair of axons
What are the two cells types that produce myelin?
Schwann cells - peripheral NS
Oligodendrocytes - CNS
[referred to as glial cells as they support the NS]
How is each axon myelinated?
They are myelinated along their lengths by chains of glial cells ( support cells )
What is the name of the gap between each myelinating cell?
Node of Ranvier
What part of the Schwann cell creates the myelin?
The membrane of the Schwann cell
Why do you end end with a lipid rich layered structure that form the myelin sheath?
Because the membrane of the Schwann cell is comprised of many phospholipids
Where is the nucleus situated in a myelinated Schwann cell?
On the outside
What is different in oligodendrocyte myelination?
They can myelinated several axons at the one time.
What is the name of the pockets of cytoplasm within the myelin sheath?
Clefts of Schmidt- Lanterman
Why is the Node of Ranvier important?
Allows ions to diffuse in and out of the axon, propagating the electrical signal down the axon and this allows for saltatory conduction
During MS, what happens the myelination of axons? And why?
It begins to degrade due to the bodies own immune system
The immune response turns against the oligodendrocytes that produce the myelin and breaks them down
Why are some axons unmyelinated
Sometimes it’s unnecessary - a short axon
How are unmyelinated axons supported?
The Schwann cell still incases the axons ( gives them a hug ) to help with their environment and maintain homeostatic level
