Myelin and Myelination Flashcards
(35 cards)
Myelin
- Lipid-rich
- Synthesised by non-neuronal cell
- Increases conduction velocity
- Loss of myelin produces neurological disorders
- Myelin may alter in learning and memory
What percentage of dry weight of white matter is myelin?
50%
Where does myelin come from in the PNS?
Schwann cells
Where does myelin come from in the CNS?
Oligodendrocytes
Schwann cells myelinate _____ axons
Individual
Oligos myelinate ______ axons/parts of axons
Several
What does myelin look like?
Protein - lipid - protein repeats
What is the periodicity of myelin in the PNS?
11.9 nm
What is the periodicity of myelin in the CNS?
10.7 nm
What percentage of myelin is water?
~40%
What percentage of myelin is dry lipid?
70-85%
What percentage of myelin is protein?
15-30%
What is myelin made of?
- Water
- Dry lipid
- Protein
PNS has less…
- Cerebroside
- Sulfatide
CNS has more…
Sphingomyelin
CNS myelin proteins
- Myelin basic protein (MBP)
- Proteolipid protein (PLP)
Proteolipid protein (PLP)
- Important role in formation or maintenance of myelin
- Mutation causes Jimpy mouse
Myelin basic protein (MBP)
- Important in myelination of nerves
- Induces experimental allergic encephalomyelitis (EAE)
- Implicated in MS
Other CNS myelin proteins
Enzymes
- Cyclic nucleotide phosphodiesterase
- Proteases
- Lipid metabolism
- Carbonic anhydrase
Ig-like molecules
- MOG and MAG
- Oligo-axon communication
PNS myelin proteins
- P0
- MBP
- PMP-22
P0
50+% of PNS myelin
MBP in PNS
Less important than in CNS
PMP-22
Alterations in gene expression associated with Charcot-Marie-Tooth 1a?
Multiple Sclerosis
- Onset 20s - 40s
- Variable severity
- May be progressive
- Plaques shown in MRI
- Primary demyelination