Somatotopy is the point-for-point correspondence of an area of the body to a specific point on the central nervous system. Typically, the area of the body corresponds to a point on the primary somatosensory cortex (postcentral gyrus). This cortex is typically represented as a sensory homunculus which orients the specific body parts and their respective locations upon the homunculus. Areas such as the appendages, digits, penis, and face can draw their sensory locations upon the somatosensory cortex. The areas which are finely controlled (e.g., the digits) have larger portions of the somatosensory cortex whereas areas which are coarsely controlled (e.g., the trunk) have smaller portions. Areas such as the viscera do not have sensory locations on the post central gyrus.
^Saladin, Kenneth (2012). Anatomy and Physiology. New York: McGraw Hill. pp. 541, 542.
^Kell CA, von Kriegstein K, Rösler A, Kleinschmidt A, Laufs H (June 2005). "The sensory cortical representation of the human penis: revisiting somatotopy in the male homunculus". The Journal of Neuroscience25 (25): 5984–7. doi:10.1523/JNEUROSCI.0712-05.2005. PMID15976087.