The spinal cord is required for a normal defecation reflex and voluntary control of the external anal sphincter (see figure 21.5). In regard to defecation, spinal cord injuries can be divided into two groups based on the level of injury : those that occur above the conus medullaris and those that damage the conus medullaris where the defecation reflex center is located. Immediately following a spinal cord injury, there is a loss of reflexes below the level of the injury, called spinal shock (see chapter 12). The reflexes usually become functional again, however, and the defecation reflex is usually depressed for a few weeks but eventually returns.