The white matter of the spinal cord contains bundles of nerves covered with a combination of proteins and fats called myelin. These bundles of nerves are called spinal tracts. Spinal tracts surround the grey matter in the center of the spinal cord and carry information to and from the brain.
Sensory spinal tracts carry nerve impulses up the spinal cord. Information about body temperature, pain, touch and pressure are conveyed to the brain through these tracts. Motor tracts convey information from the brain, through the spinal cord and out to the skeletal muscles. Controlled movement of the body is achieved by impulses conveyed through motor tracts.