Oligodendrocytes are glia of the central nervous system named from Greek words for cells with a few branches. They have a soma and up to a few dozen processes.
The membrane of the end of each process wraps thinly around an axon many times like a roll of tape. This membrane is a material called myelin that is composed mostly of lipid, which insulates the axon like the rubber coating on a wire.
Each oligodendrocyte process forms one segment of myelin on one axon, and each process may myelinate different axons.
In addition to the function of myelination, oligodendrocytes also appear to influence neurons and other glia, and vice versa, through exchange of a variety of substances. There are also some oligodendroctyes, called nonmyelinating because they do not appear to myelinate axons. These are variably shaped, and their function is not clear.
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Thank you for this, I’ll be returning often, I suspect!
With regard to Oligodendrocytes, I am specifically confused as to how many segments on the SAME axon one oligodendrocyte can myelinate.
You say, “Each oligodendrocyte process forms one segment of myelin on one axon, and each process may myelinate different axons.” One segment on ONE axon. That looks to me like you mean one segment PER axon. Yet your drawing shows an oligodendrocyte making multiple segments on the SAME axon. I get that an oligodendrocyte can myelinate multiple axons, but can one oligodendrocyte myelinate multiple segments on the SAME axon?
Would it be more correct to say that each oligodendrocyte process forms one segments of myelin, and each oligodendrocyte can ((or will?)) send multiple processes to myelinate segments on multiple different axons, as well as multiple processes to myelinate multiple segments on the same axon ?
And you also say that each PROCESS may myelinate different axons; but isn’t it that each OLIGODENDROCYTE, not each PROCESS, can myelinate different axons?
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You are welcome, and great questions:
“Would it be more correct to say that each oligodendrocyte process forms one segments of myelin, and each oligodendrocyte can ((or will?)) send multiple processes to myelinate segments on multiple different axons, as well as multiple processes to myelinate multiple segments on the same axon?” – Yes, that is my understanding.
“And you also say that each PROCESS may myelinate different axons; but isn’t it that each OLIGODENDROCYTE, not each PROCESS, can myelinate different axons?” – Yes, I totally agree, and sorry for any confusion.
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Thank you Matthew, for both your work on this, and for your reply to me! It really helps me to find out that what I THINK I understand about either neuroscience or brain anatomy are sometimes correct! I look at every website on the subjects & some books to try to put together the best picture I can arrive at in summation (a neuro joke?), and most times that I see possibly confusing information (& I often get confused!) I try to ask questions, so it really helps to have my questions answered & this confusion resolved, thank you!
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