Function

As already described, two nerve tracts originate from the spinal cord on each side and level, which only after a short time unite to form a spinal nerve. These rear and front nerve roots carry different qualities of nerve fibers. While the front nerve roots send motor impulses from the brain to the muscles, the rear nerve roots send sensitive impulses, such as information regarding our sensation of touch and temperature, to the spinal cord.

Here they are transferred to a second nerve cell and transmitted to the brain. The nuclei of the sensitive nerve fibers lie exactly in the intervertebral hole and form a roundish expulsion of the nerve, the so-called spinal ganglion. To facilitate naming the various nerve fibers within a single nerve, they are differentiated according to their direction of progression.

Regardless of where exactly they run in the body and what quality of information they carry, nerve fibers running to the brain are generally referred to as afferent and nerve fibers running away from the brain as efferent. The nerve roots thus fulfill the function of conducting information from the rest of the body to the brain and from the brain to the body. The peripheral body is systematically assigned to the respective spinal nerves.

This is very clearly illustrated by the nerve supply to the skin. If you imagine a person sitting upright with arms and legs stretched out straight forward and then draw lines between the supply areas of the individual spinal nerves, you can see that these supply areas largely form precisely drawn cross-stripes. They even form almost perfect rings around the trunk.

These skin supply areas of the spinal nerves are called dermatomes. The muscles under the spinal nerves are also divided less clearly, but also very systematically. The knowledge of these supply areas is of enormous importance for the diagnosis of herniated discs and other nerve root irritations.Thus, pain, sensory disturbances or muscle weakness caused by these diseases always occur in the area or muscle supplied by the irritated nerve. Complaints caused by damage to or irritation of a nerve root are called radicular (from Latin radix = root).