Glia Flashcards
Ratio of glia:neuron
10:1
Resident macrophages of the brain
Microglia
Glia cell that makes myelin in PNS
Schwann cells
Glia cell that make myelin in CNS
Oligodendrocytes
Neural tube origin (3)
Oligodendrocytes, Astrocytes, and neurons
Neural crest origin (1)
Schwann cell
(Oligo/Schwan cells) can differentiate without neuronal signals, while (oligo/schwann cell) needs neuronal signals to differentiate
Oligos don’t need signal, schwann need signal
Myelin is an extension of?
Plasma membrane of schwann cells/ oligodendrocytes
Which cell (and where) can insulate up to 40 different axon segments?
Oligos, in CNS
Which cell (and where) can insulate ONLY ONE axon segment?
Schwann cell, in PNS
These cells form Remak bundles around neurons
Non-myelinating Schwann cells (Sensory C-fibers)
Molecular architecture of compact myelin consist of these two lines
Intraperiod lines (between membranes, external layer) Major dense lines (membrane, cytoplasmic part)
This protein holds internal surfaces together and seal up the major dense lines
Myelin basic protein (MBP)
This protein involved in keeping myelin sheath compact is only found in CNS
PLP
This protein involved in keeping myelin sheath compact is only found in PNS
PMP22
This lipid has a major role in keeping myelin compact
Glycosphingolipids (GSL)
Mutations in these components of compact myelin result in many different disorders
PLP - Pelizaeus Merzbacher Disease
PMP22, P0, Cx32 - Charcot marie Tooth Disease
GSL- Leukodystrophies (lipid storage diseases)
What is the percent composition of lipid and protein in CNS myelin? How does this compare to entire brain?
CNS myelin- 70% lipid, 30% protein
Whole brain- lipid < Protein
Channels that transverse through myelin
Schmidt-Lanterman cleft
Site of myelin attachment to the axon, found next to Nodes of Ranvier, where myelin loops get attached
Paranodal region
In addition to Schwann cells, what else covers some of myelin in PNS?
Microvilli
There are no microvilli present in CNS; what instead covers the nodal region?
Astrocytes, function still unclear
Three important molecules that are important in myelin-axon interaction. What happens if these are removed?
Caspr, Lipids, NF155.
If ands not formed, paranodes to not form resulting in bad connection with neurons. Shaking
In addition to increasing nerve conduction velocity and saltatory conduction (propagation of action potential), what are two other functions of myelin?
- Bi-directional signaling
2. Inhibits axon regeneration (CNS myelin) - not good!
Glia to neuron interaction
Bi-directional signaling
Two things that inhibit regernation of axons in CNS
- degenerating myelin- produce inhibitory signals
2. Astrocytes- come in and make scars
Lack of axon regeneration is a major problem in these type of injuries
Spinal cord injury,