The spinal cord is an integral part of the body's communication system. Comprised primarily of the brain, spinal cord, and a massive system of sensory receptors, the central nervous system is responsible for processing internal and external communications. In terms of the specific function of the spinal cord in the central nervous system, it is a direct link between the brain and other body systems. Information flows in from nerves throughout the body, traveling along the spinal cord to the brain. Once information is received, the brain processes it and sends out messages along the spinal cord to initiate the appropriate system responses.
To fully understand the role of the spinal cord in the central nervous system, it is necessary to first understand its construction. Inside the spine, the spinal cord is comprised of a bundle of separate nerves, wrapped together like a cable. Measuring roughly 16 inches (40.64 cm) long and less than 1 inch (approximately 2 cm) wide, the spinal cord connects to the brain and extends the full length of the backbone. It is protected by fluid-filled membranes known as the meninges, which are further protected by the backbones that surround the spinal column.
At several points, the spinal cord branches out into nerve pairs that communicate information to and from four separate regions of the body: the cervical, thoracic, lumbar, and sacral regions. These innervated areas facilitate communications from various body parts and systems along the spinal cord, up to the brain, and then back again. For example, the cervical region relays information to and from the head, neck, arms, and hands. Comparatively, the thoracic regions relays information to and from the heart, chest, and other systems within the abdominal area of the body. Without the use of the spinal cord in the central nervous system, the brain would have no way to receive information from these outlying body regions.
Disease or injury to the spinal cord cuts off communications between the brain and body regions, much like cutting a telephone line disconnects a call. When an injury occurs, for example, the role of the spinal cord in the central nervous system is compromised. Severe spinal cord injuries, such as seen in paraplegics, can cause such a disruption in the central nervous system that the brain is no longer able to control various muscles and tendons. While the body systems and the brain may continue to send out the proper signals and messages, the main communication line is damaged so messages cannot get through.