Nerve supply to the skin the kind of sensory inputs which project to a specific region of the primary somatosensory cortex. Groups of nerve terminals located in the different layers of the skin are categorized depending on whether the skin is hairy, nonhairy, or an exposed mucous membrane. The hairy parts of the body such as the forearm or the leg have two groups of nerve endings: those that end along with the hair follicles, and also with the arborizations of unmyelinated axons which are referred to as “free” nerve endings because they are served by both myelinated and unmyelinated axons. Nonhairy skin, such as
Nerve supply to the skin the most densely innervated parts of the body. Though there is no specific categorization, both “free” nerve endings and unencapsulated nerve endings of myelinated axons are found within the dermis of those areas. The cornea, one of the other exposed mucous membranes, contains “free” nerve endings served by nonmyelinated axons. The conjunctiva contains a less dense distribution of “free” nerve endings that are served by both myelinated and unmyelinated axons. The distribution of the sensory neurons within the skin accounts for the large and overlapping receptive fields of the skin. The size of the receptive fields in turn explains why