Touch is made up of several skin sensations — pressure, warmth, cold, and pain — each detected by skin receptors that transduce stimulation into neural signals.
The skin can be fooled: when warm and cold receptors fire at the same time, the brain reads the combination as hot.
Pain protects us by warning of harm; people born unable to feel pain often suffer serious injuries.
Gate-control theory says a neurological gate in the spinal cord can pass or reduce pain signals; touch signals like rubbing, or signals from the brain, can help close it.
The brain can also create pain without any body signals, as in phantom limb sensation.
Pain is not a direct readout of injury; attention, expectations, emotions, past experiences, and placebos all affect how intensely it is felt.
Key terms
skin senses
The sensations that make up touch: pressure, warmth, cold, and pain.
pain receptors
Receptors in the skin that detect harmful stimulation, like extreme heat or tissue damage.
gate-control theory
The theory that a neurological gate in the spinal cord either lets pain signals reach the brain or reduces their transmission.
phantom limb sensation
Sensations, including pain, that seem to come from a missing limb but come entirely from the brain.
placebo
A treatment with no active ingredient; simply expecting it to work can reduce pain.
Watch out
The pain gate can be closed from below (touch signals like rubbing) or from above (the brain), and the brain can even create pain with no body signals.