Nerve: Glossary Definition

Nerve: definition - Specialized cord-like tissue that transmits signals to and from the brain.

Patients with chronic back pain or muscular weakness related to a back condition are probably familiar to the term nerve as it relates to their own back pain. You will probably have heard the term nerve pain or nerve damage as applied to your medical condition, either in the diagnosis of your condition or to rule out the cause of your problem. Back pain may be caused by a number of factors, including bone damage, muscle pulls and strains, and sprains of the soft tissue (ligaments and tendons) that supports the parts of the spine and musculoskeletal system. But while the bones, soft tissues, and muscles may become strained and injured, due to trauma and disease, they are remarkably resilient, and many of these structures can heal themselves. The structures that have less of an ability to heal themselves, though, are the nerves which branch off of the spinal cord and travel throughout the body. Nerve pain and nerve damage are typically responsible for many of the cases of severe back pain, chronic back pain, and pain that includes associated neurologic symptoms. These neurologic symptoms may include muscular weakness, the loss of bladder/bowel control, numbness, burning, and radiating pain down the arms and legs. Back pain with associated symptoms related to nerve disease and pressure on the nerves (nerve compression) require the most attention of the doctors because they can lead to significant loss of body function and back pain that approaches unbearable levels.

The nerves are extensions of the brain and spinal cord, which are the main centers of the body that send, receive, and interpret the neurologic signals of the body. Together, the brain and spinal cord contain all of the nerves and neurons of the central nervous system. The brain is the main integrating center of all of the nerve signals in the body, and sends and receives information from the spinal nerves in the spinal cord. The spinal nerves exit the spinal cord, where they become part of the peripheral nervous system. The nerves that exit through openings in the spine are known as nerve roots. These nerve roots branch hundreds of times after they exit the spine, to the point that nearly every cell in the body is closely located to a nerve fiber. The nerves of the peripheral nervous system supply information that controls its two subdivisions: the somatic nervous system and the autonomic nervous system.

The somatic nervous system consists of all the nerves and nerve fibers that supply information to our skeletal muscles, which are the muscles that we consciously use to walk and move. The autonomic nervous system consists of all the nerves and nerve fibers that control the smooth muscles of our organs and the body structures that function automatically (e.g. digestive system, mechanisms for maintaining heart rate and body temperature, etc.) If the nerves of our body become squeezed or damaged, in any way, both conscious motor control and these autonomic body processes may be hindered, to some extent. This is the reason why nerve damage is suspected in back pain conditions where the patient also experiences neurologic symptoms such as numbness or weakness in the legs (sciatica).

Form and Function of a nerve. A nerve has two main structures that are involved in the function and maintenance of the structure responsible for sending information to and from the spinal cord. The basic unit of the nerve is the neuron. The core element of the neuron is the soma, which received information from fingerlike fibers called Dendrites, and transmits information through its Axon. The soma is also called the neurosoma, cell body, or perikaryon. The soma has a single, centrally located nucleus with large nucleolus. The axon is the cable-like structure that transmits the electrical signals. The axon is surrounded by structures called Schwann cells and Myelin sheaths, which protect the cells and increase the speed with which the electrical signals travel along the axon.

The nerves of the spinal cord and peripheral nervous system consist of bundles of these nerve fibers.