Myelin (Gr. Myelos - Bone Marrow)

Myelin (from the Greek myelin, meaning "bone marrow") is a fat-like substance that forms sheaths around the axons of nerve cells in the central nervous system and some peripheral nerves. This sheath, called the myelin sheath, serves to protect and speed up the transmission of nerve impulses.

Myelin is produced by special cells - oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. Myelination is the process of formation of the myelin sheath around the axon, which begins at birth and continues throughout a person's life.

The myelin sheath is composed of several layers of phospholipids and proteins that give it fat-like properties. It wraps the axon, forming many separate segments, separated by areas without myelin - nodes of Ranvier. These nodes of Ranvier play an important role in the transmission of nerve impulses, as they allow the impulse to quickly jump from one segment of the myelin sheath to another.

Myelin is of great importance for the normal functioning of the nervous system. Some diseases, such as multiple sclerosis, are characterized by impaired myelination and destruction of the myelin sheath. This disrupts the transmission of nerve impulses and can cause various symptoms such as weakness, paralysis and sensory disturbances.

Overall, myelin is an important component of the nervous system that allows for the rapid and efficient transmission of nerve impulses. Its loss or damage can lead to serious disruptions to the functioning of the nervous system and cause various diseases.