Certain types of neurons are surrounded by special cells, Schwann cells.
These cells coil dozens of times around the axon and form a membranous layer called the myelin sheath.
The myelin sheath acts as an electrical insulation and increases the velocity of nerve impulse propagation along the axon.
In degenerative disease known as multiple sclerosis, for example, a gradual deterioration of the myelin sheath occurs, resulting in progressive loss of nerve coordination.
Nervous tissue has other helper cells that support the functioning of the nervous system: these are glial cells or glial cells. They differ in form and function, each playing a different role in the structure and functioning of nervous tissue.
Astrocytes provide mechanical support and feed the complex and delicate network of nerve circuits. Oligodendrocytes perform the same function as Schwann cells, forming protective sheaths on neurons in the brain and spinal cord. Microglia are a specialized type of macrophage whose function is to phagocyte debris and cellular debris present in nervous tissue.