Somatosensory system

The somatosensory system is the sensory system of somatic sensation.

A more complex concept comes into play when the term is used in reference to human beings. The sense of touch is mediated by the somatosensory system. Touch may simply be considered one of five human senses; however, when a person touches something or somebody this gives rise to various feelings: the perception of pressure (hence shape, softness, texture, vibration, etc.), relative temperature and sometimes pain. Thus the term "touch" is actually the combined term for several senses. In medicine, the colloquial term "touch" is usually replaced with somatic senses, to better reflect the variety of mechanisms involved.

Somatic sensation consists of the various sensory receptors that trigger the experiences labelled as touch or pressure, temperature (warm or cold), pain (including itch and tickle), and the sensations of muscle movement and joint position including posture, movement, and facial expression (collectively also called proprioception).

The primary somatosensory area in the human cortex is located in the postcentral gyrus (Parietal Lobe). Areas of this part of the human brain map to certain areas of the body, dependent on the amount or importance of somatosensory input from that area. For example, there is a large area of cortex devoted to sensation in the hands, while the back has a much smaller area. This somatosensory map is termed the homunculus.

The somatosenses include: Cutaneous (skin), kinesthesia (movement) and organic senses, of which the first two are better known. Organic senses have to do with sensory information from the organs, such as stomach aches.