|
In medicine, the term "touch" is usually replaced with "somatic senses" to describe the variety of senses involved. Although touch (also called tactile perception) is considered one of the five traditional senses, the impression of touch is formed from several sensations including pressure, skin stretch, vibration and temperature. The somatosensory system is a complex sensory system. It is made up of a number of different receptors, including thermoreceptors, photoreceptors, mechanoreceptors and chemoreceptors. It also comprises essential processing centres, or sensory modalities, such as proprioception, mechanoreception (touch), thermoception (temperature), and nociception (pain). The sensory receptors cover the skin and epithelial tissues, skeletal muscles, bones and joints, internal organs, and the cardiovascular system. Somatic senses are sometimes referred to as somesthetic senses, with the understanding that somesthesis includes touch, proprioception and (depending on usage) also haptic perception. Processing primarily occurs in the primary somatosensory area in the parietal lobe of the cerebral cortex: information is sent from the receptors via sensory nerves, through tracts in the spinal cord and finally into the brain. The system works when activity in a sensory neuron is triggered by a specific stimulus such as pain, for instance. This signal then passes to the part of the brain attributed to that area on the body—this allows the stimulus to be felt at the correct location. The mapping of the body surfaces in the brain is called a homunculus and plays a fundamental role in the creation of body image. This brain-surface ("cortical") map is not immutable, however. Dramatic shifts can occur in response to stroke or injury. ==Structure== The somatosensory system is spread through all major parts of a mammal's body (and other vertebrates). It consists both of sensory receptors and sensory (afferent) neurons in the periphery (skin, muscle and organs for example), to deeper neurons within the central nervous system. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Somatosensory system」の詳細全文を読む スポンサード リンク
|