Glial Cells Support Neurons

All information both to and from the body must be coordinated and transmitted simultaneously and very quickly. The brain itself requires extremely fast speeds to operate at even at the simplest level. How do the biological tissues of our body support such rapid coordination of the brain, limbs, and sensory input? They do so with nervous system tissue that imitates electrical wiring.

A series of photomicrographs and schematic illustrations show myelinated nerve fibers. Panel A is an illustration of a single neuron with major structures labeled. Panel B is an illustration of a cross section of a neuron that shows a myelin sheath wound around an axon. Panel C shows a cross section of a nerve stained with toluidine blue and viewed with a light
These cells communicate with each other to perform important tasks in the nervous system. The glial cells support neurons structurally and maintain their long-term neuronal integrity, and neurons regulate glial cell behavior. In this support of neurons, glial cells have become highly specialized. Glial cells, which can be divided into several types, have various important functions, such as providing structural support, growth support, and insulation around the axon.

Why must glial cells support neurons? Neurons are specialized cells that receive and send signals to other cells through fragile and thin cellular extensions called axons. These axons extend over distances long and short to reach their target, ultimately connecting neurons with other nerve tissue, muscle tissue, or sensory organs (Figure 1A). For example, some motor neurons in the spinal cord have axons that exceed 1 m in length, connecting the spine to the lower limb muscles. These axons transmit signals to the target muscle in the form of electric impulses called action potentials. However, the axons alone are not enough to produce rapid conduction of the electric current necessary for this signal to be sent. Glial cells are the key element for supporting the messages neurons send and receive all over the body. Much like the insulation around the wires in electrical systems, glial cells form a membraneous sheath surrounding axons called myelin, thereby insulating the axon. This myelination, as it is called, can greatly increase the speed of signals transmitted between neurons (known as action potentials). Indeed, the evolution of myelin allowed vertebrates to achieve efficient nervous systems despite their large body