How We Sense the World and Control Movement

Specialized neurons carry messages about pain, temperature, touch, vibration, and proprioception from the skin, muscles, joints, and internal organs to the spinal cord. Once there, the messages are relayed to the brain and to local circuits in the spinal cord that control reflexes, like pulling your hand away from a hot flame. Two pathways carry information from the spinal cord to the brain. The spinothalamic tract carries messages about pain, temperature and touch. The lemniscal pathway carries messages about deep touch, pressure, touch location (also called two point discrimination), vibration, and conscious proprioception. These pathways are in different locations in the spinal cord, so an injury might not affect them in the same way or to the same degree.

Each segment of the spinal cord contains the sensory inputs from a particular region of the body. Scientists have mapped these areas out and determined where the receptive fields are for each level of the spinal cord. A receptive field from one level of the spinal cord is called a dermatome. Neighboring dermatomes overlap each other, so the lines on the diagram are artificial, but they do show which level of the cord is connected to which level of the body.