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, 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
Touch is perceiving the environment using skin. Specialized receptors in the skin send signals to the brain indicating light and soft pressure, hot and cold, body position and pain. It is a subset of the sensory nervous system, which also includes the visual, auditory, olfactory, gustatory and vestibular senses.
In physiology touch is called the Somatosensory system, a network of neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position (proprioception), and pain (nociception).
Somatosensation begins when mechano- and thermosensitive structures in the skin or internal organs sense physical stimuli such as pressure on the skin (see mechanotransduction, nociception). Activation of these structures, or receptors, leads to activation of peripheral sensory neurons that convey signals to the spinal cord as patterns of action potentials. Sensory information is then processed locally in the spinal cord to drive reflexes, and is also conveyed to the brain for conscious perception of touch and proprioception. Note, somatosensory information from the face and head enters the brain through peripheral sensory neurons in the 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 cerebral cortex in the brain represent nearby locations on the skin or in the body, creating a map, also called a cortical homunculus.