Touch
Touch is one of the body's senses, provided by the skin. We normally think of the sense of touch being only in the fingers, but most parts of the skin are capable of feeling and perceiving various elements of this sense.
Strictly, touch is part of the somatosensory system that perceives what we call “touch” or “pressure” including vibration, temperature (warm or cold), pain (including itch and tickle), as well as proprioception (the sensations of muscle movement and joint position including posture), movement, face | facial expression and visceral senses (sensory information from within the body, such as stomach aches).
Through a combination of these senses, generally using the fingers and arms, we are also able to perceive shape, softness, and texture.
Touch is important to blind people who typically use touch in combination with hearing to determine the shape of the world around them.
- Snippet from Wikipedia: Somatosensory system
The somatosensory system, or somatic sensory system is a subset of the sensory nervous system. It has two subdivisions, one for the detection of mechanosensory information related to touch, and the other for the nociception detection of pain and temperature. The main functions of the somatosensory system are the perception of external stimuli, the perception of internal stimuli, and the regulation of body position and balance (proprioception).
Mechanosensory information includes that of light touch, vibration, pressure and tension in the skin. Much of this information belongs to the sense of touch which is a general somatic sense in contrast to the special senses of sight, smell, taste, hearing, and balance.
Nociceptory information is that received from pain and temperature that is deemed as harmful (noxious). Thermoreceptors relay temperature information in normal circumstances. Nociceptors are specialised receptors for signals of pain.
The sense of touch in perceiving the environment uses special sensory receptors in the skin called cutaneous receptors. They include mechanoreceptors such as tactile corpuscles that relay information about pressure and vibration; nociceptors, and thermoreceptors for temperature perception.
Stimulation of the receptors activate peripheral sensory neurons that convey signals to the spinal cord that may drive a responsive reflex, and may also be conveyed to the brain for conscious perception. Somatosensory information from the face and head enter the brain via cranial nerves such as the trigeminal nerve.
The neural pathways that go to the brain are structured such that information about the location of the physical stimulus is preserved. In this way, neighboring neurons in the somatosensory cortex represent nearby locations on the skin or in the body, creating a map or sensory homunculus.