Neurons have a very important and complex task, that would be nearly impossible to accomplish alone. To assist them in their task there are 6 specialized cells who's main function is to support neurons, and neural activity. These smaller cells surround and wrap or support and protect the delicate neurons. The 4 supporting cells of the CNS are collectively called neuroglia or glial cells. The supporting cells in the CNS outnumber the actual neurons 9 to 1.

Microglia are supporting cells that protect the nervous system by destroying invasive microorganisms and other materials that could be harmful to the system. Microglia are actually a special form of macrophage (a type of white blood cell involved in fighting infection and protecting the body.), oval in shape with thorny processes. As such these cells are actually derived from a blood cell called a monocyte.

Astrocytes are the most abundant of all supporting cells in the CNS. This maybe because they play so many vitally important and diverse roles in the maintenence of the nervous system. They have many radiating projections which attach themselves to neurons and capillaries. By doing this they anchor and brace the neurons in their given position and act as nutrient pathways for the neurons, who through the astrocytes, recieve some of their neccessary nutrients from the blood traveling in the capillaries. Astrocytes are also responsible for maintaining an ideal chemical environment for the neurons. They do this by absorbing harmful, or disruptful chemicals in the environment such as excess potassium. They are thought to communicate with each other via intracellular calcium pulses and are known to assist the immune response by acting as antigen presenting cells. To do this the astrocytes display a portion of a foreign antigen on a special protein on their surface called a MHC. This acts as a flag for white blood cells, telling them that there is an invader in the system, and what that invader is.

Ependymal cells are cells that line the central cavities of the brain and spinal cord. They are ciliated and act as a semi-permeable lining between the cavities and normal tissue. The cavities are filled with a cerebro-spinal fluid which cushions the CNS and, due to the beating cilia of the ependymal cells, is constantly circulating.

Oligodendrocytes are branching cells that wrap themselves around axons to form myelin sheaths in th CNS. This is a very simple yet extremely important job, which is discussed in other sections.

The next two cells are associated with the PNS. Schwann cells are very similar, functionally, to oligodendrocytes, as they are responsible for myelin sheath formation in the peripheral nervous system. Schwann cells however also function as phagocytes (similar to microglia), by engulfing deteriorating cell debris and are vital to the process of peripheral nerve fiber regeneration.

The second type of supporting cells for the PNS are called satellite cells. They surround the neural cell bodies in ganglia, and are responsable for regulating and maintaining the chemical environment of the neuron.

Myelin sheaths are found only on axons of nerve cells in both the PNS and the CNS. Myelination, a form of insulation, increases the speed of action potentials along an axon. It does this so well that myelinated cells have action potentials up to 150 times faster than unmyelinated cells. In the PNS, Schwann cells grow in a spiral around an axon. As they grow they continue to wrap around the axon. The outer most layer of this cell wrap, is called the neurilemma, and contains the cell's organelles. The rest of the cells plasma membrane is lacking many of the membrane proteins common to most cells. Because of this, the axon is surrounded at these myelination points by tightly packed concentric layers of organic membrane which are impermeable to most ions and insulates the axon at that particular point. Myelin increases the membranes capacitance, or ability to keep ionic charge seperate. These myelin sheaths are evenly spaced along the axon and there is a small gap of unmyelinated axon between each sheath. These evenly spaced spots of bare axon are called nodes of Ranvier, or neruofibril nodes. These breaks in myelination are what increase the speed of the action potential, for they cause the action potential to "jump" from node to node. Myelination in the CNS is very similar except that oligodendrocytes are responsible for the myelination. However where one Schwann cell makes one sheath, oligodendrocytes are able to make multiple sheaths around multiple axons. This is because the actual cell does not wrap around the axon, only the processes (extensions or "arms") of the cell actually wrap around the axon. This leaves the cell body unwound about any single axon and connected to many via it's processes. Because of this, CNS myelin sheaths lack a neurolemma, and the nodes of Ranvier are generally more widely spaced. Sometimes however Schwann cells and oligodendrocytes wrap around an axon and "embrace" it, yet there is no coiling around it. These axons behave as if they are uninsulated at that point, and are thus recognized as unmyelinated with regards to that area.