Four kinds of touch receptor, the Piezo2 channel behind the 2021 Nobel Prize, the pathways to the brain and the sensory homunculus — how skin becomes a sense.
Senses & Perception
Beginner
Touch and the Somatosensory System
The Editors
April 11, 2026
3 min read
In plain English
Your skin contains several kinds of touch sensors — some for light touch, some for vibration, some for stretch. They send signals up the spinal cord to a strip of brain called the somatosensory cortex, which has a map of the whole body. Fingertips and lips have the most sensors and the most brain space.
Beginner level: No background needed. Everyday language, everyday examples — the place to start.
Concepts to know first
Go deeper next
The somatosensory system covers touch, pressure, vibration, temperature, pain, itch and the sense of body position. It is spread across the whole body, which makes it the largest sensory system.
Four kinds of touch receptor
The smooth skin of your fingertips contains four main types of mechanoreceptor, each with a different specialty. Meissner corpuscles respond to light touch and slipping — vital for grip. Merkel cell complexes respond to sustained pressure and fine texture and edges, such as Braille dots. Pacinian corpuscles, onion-like structures deeper in the skin, respond to high-frequency vibration. Ruffini endings respond to skin stretch. Hairy skin also has receptors wrapped around hair follicles, and slow, unmyelinated C-tactile fibres that respond best to gentle stroking at about the speed of a caress — thought to underlie pleasant, social touch.
The molecule of touch
How does pressure become an electrical signal? In 2010 Ardem Patapoutian's lab identified Piezo ion channels, which open when the cell membrane is stretched. Piezo2 is the main touch and proprioception sensor; people born without working Piezo2 have severely impaired touch discrimination and body-position sense. Patapoutian shared the 2021 Nobel Prize with David Julius, who discovered heat receptors.
Pathways and the body map
Touch and body-position signals travel up the back of the spinal cord (the dorsal columns), cross over in the brainstem, relay in the thalamus, and arrive at the primary somatosensory cortex in the parietal lobe. Pain and temperature take a different route that crosses in the spinal cord. The cortex holds a body map — the sensory homunculus — with large areas for the hands, lips and tongue, which have the densest receptors.
Touch and wellbeing
Touch is essential for development. Skin-to-skin contact ("kangaroo care") benefits premature babies, and classic (now ethically troubling) studies by Harry Harlow found infant monkeys preferred a soft cloth "mother" to a wire one that provided food.
Everyday examples & things to try
Try it
The two-point test
Have a friend touch your skin with either one or two pencil points while your eyes are closed. On your fingertip you can detect two points only a few millimetres apart. On your back, they may need to be several centimetres apart before you feel two. That difference mirrors receptor density and the size of each body part's area in the somatosensory cortex.
Key takeaways
- Meissner, Merkel, Pacinian and Ruffini receptors detect different features of touch.
- The Piezo2 channel is the key molecular touch sensor (Nobel Prize 2021).
- Touch signals reach a body map in the somatosensory cortex, largest for hands and lips.
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