[Igor (OP)]

Does myelin exist other than on neurology ?

[chris]

Absolutely. Myelin is the name given to a fatty layer of insulation wrapped around nerve fibres in both the central and peripheral nervous systems. This myelin sheath dramatically increases the speed at which information travels along nerves (by a factor of six-fold or more).

Myelin is formed when a nerve axon comes into contact with a myelinating cell. In the brain and spinal cord this is an oligodendrocyte, so named because the same cell provides myelin to several nerve fibres at once. In the peripheral nervous system (the nerve supplying skin, muscles, blood vessels and the guts) the job is done by schwann cells, which each myelinate only a single axon.

When these myelinating cells contact a nerve axon the cell wraps itself around the axon multiple times, building up thin layers of cell membrane, as this electronmicrograph (from the University of Texas, Galveston) shows:

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Not all nerve fibres are myelinate - the smallest calibre "C" fibres, which convey pain and temperature sensations, are unmyelinated and conduct information considerably more slowly as a consequence (about 1 m/s compared with 6 m/s for a myelinated fibre of the same calibre).

Chris

[Igor (OP)]

Hi Chris,
in response to the question "Does myelin exist other than on neurology ?"
you replied "Absolutely", but then only described myelin on the nervous system.

My question was does myelin exist in the body other than on the nerves,
i.e. does it only exist on neurology ?.

An additional myelin question, could you please tell me,
what is the total thickness of the seven layers of myelin in the above electronmicrograph? (approximately).