Every sensation of pain you have ever experienced — a stubbed toe, a headache, a paper cut — is ultimately registered and produced by your brain. And yet the brain's own tissue contains no pain receptors (nociceptors) at all. Surgeons can cut, prod, or electrically stimulate the surface of a living, conscious brain, and the patient feels nothing from the brain tissue itself — a fact anatomy makes possible, and neurosurgery has put to direct, practical use.
Where the sensation actually comes from
Pain is registered when nociceptors — nerve endings specialised to detect tissue damage or potentially damaging stimuli — send signals through the nervous system to be processed and consciously experienced. Nociceptors are distributed throughout skin, muscle, joints, and most internal organs, but the brain's own neural tissue lacks them entirely. What a "headache" actually registers is pain from structures around the brain rather than the brain itself: the meninges (the brain's protective membranes), blood vessels, and muscles and tissues of the scalp and skull all carry nociceptors and are the true sources of head pain, even though the sensation is, in every case, ultimately processed by the very organ that can't itself feel anything.
Why this makes "awake" brain surgery possible
Because brain tissue itself carries no pain receptors, once a surgeon has anaesthetised the scalp and skull — the parts that actually can feel pain — a patient can, for procedures where it's medically useful, remain conscious while the surgeon works directly on brain tissue. Awake craniotomy is used specifically for surgery near regions responsible for language, movement, or other critical functions: keeping the patient awake and responsive lets the surgical team ask them to speak, move, or perform tasks in real time, directly testing which brain regions are safe to operate near and which must be avoided, in a way that wouldn't be possible under general anaesthesia. The patient feels the incision and manipulation of the skull and its coverings, all of which are numbed, but reports nothing at all when the brain tissue itself is touched, cut, or stimulated.
What we're still unsure about
The absence of nociceptors in brain tissue itself, and the location of pain-sensitive structures around it, is well established anatomy, not a matter of dispute. What remains genuinely less settled is the broader question of exactly how the brain converts nociceptive signals arriving from elsewhere in the body into the subjective experience of pain — a process that clearly involves far more than simple signal relay, since factors like attention, emotional state, and expectation measurably change how much pain a person reports from an identical physical stimulus. Precisely how and where in the brain that subjective, felt quality of pain actually arises from underlying neural activity remains one of the harder open problems in neuroscience.
This sits inside Neuroanatomy & the Brain, one of seven topics in Anatomy, one of four domains in Medicine, one of seventeen subjects the app can quiz you on.