JARGON BUSTER

CAPSAICIN

This chemical, found in chillies, binds to a nociceptor that also responds to extreme heat. This is why biting into a chilli can cause pain.

NOCICEPTORS

These are receptors on the pain nerve fibres that act like a lock. Certain keys (irritants, mechanical forces, temperature) open them and set offff messages to the brain, signalling pain and tissue damage. Over-the-counter painkillers target nociceptive pain.

PAIN NERVE FIBRES

A, (A-delta) and C fibres are nerves that carry signals from nociceptors in the skin, muscles and joints to the spinal cord.

PHANTOM PAIN

This is the perception of pain in a limb or organ that’s missing. This most often occurs following the amputation of an arm or a leg. It’s devastating for patients, and some theories suggest that it’s a result of altered nerve signals in the brain trying to ‘ fill the gap’.

PLACEBO ANALGESIA

Placebos are substances with no active therapeutic effect. Patients who take them often report improvements in their condition. Placebo analgesia is pain relief from, say, a sugar pill, and neuroimaging has shown that it can work by hijacking an old and inbuilt ‘ free pain relief’ system in the brain.