In physiology, nociception, also nocioception; from Latin nocereĀ 'to harm/hurt') is the sensory nervous system's process of encoding noxious stimuli. It deals with a series of events and processes required for an organism to receive a painful stimulus, convert it to a molecular signal, and recognize and characterize the signal to trigger an appropriate defensive response.
Mechanism of nociception via sensory afferents
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.
Touch is a crucial means of receiving information. This photo shows tactile markings identifying stairs for visually impaired people.
Touch can result in many different physiological reactions. Here, a baby laughs at being tickled by an older sister.