The spinal cord sends messages from the brain to other parts of the body and from other parts of the body to the brain, says the University of Alabama Birmingham School of Medicine. As such, the spinal cord is part of the central nervous system.
The spinal cord also mediates the peripheral nervous system, which passes out from the spinal column through foraminae, which are openings in the bones of the spinal column, or vertebrae, claims SpineUniverse. The nerves come in pairs, with one nerve in control of voluntary motor functions and the other in control of sensory functions such as the sensations of pain, pressure, touch, hot and cold. The spinal cord also controls autonomic functions. These functions are those not under the person's conscious control such as digestion, blood pressure, body temperature and heart rate.
The spinal cord itself is a tube around 18 inches long, says SpineUniverse. It is packed with nerve bundles and fed and lubricated by cerebrospinal fluid. The vertebrae give the spinal cord protection, as do the three layers of the meninges. The outer layer is called the dura mater, the middle layer is the arachnoid mater and the inner layer is the pia mater.