Nervous system ↗Nociceptors transduce threat
Free nerve endings respond to intense mechanical, thermal, and chemical conditions and to mediators released during tissue injury or inflammation.
BRAIN & NERVES / 07
Nociception travels.
Pain is constructed.
Nociceptors detect potentially damaging conditions, but pain is a real percept emerging from distributed sensory, emotional, cognitive, autonomic, and contextual processing. Signals are modulated at peripheral, spinal, brainstem, and forebrain levels.
Peripheral fibers conduct
Myelinated A-delta and unmyelinated C fibers differ in conduction and response properties; categories overlap more than a simple “fast versus slow pain” label.
Dorsal horn integrates
Primary afferents release transmitters onto spinal neurons and interneurons. Touch, local inhibition, inflammation, and descending input can change transmission.
Ascending routes distribute
Anterolateral pathways reach brainstem, thalamic, hypothalamic, limbic, and cortical networks supporting localization, salience, arousal, emotion, and action.
Pain is not a tissue meter
Attention, expectation, prior learning, mood, sleep, social context, threat, safety, and competing needs can change pain without making it imaginary.
Brainstem pathways set gain
Periaqueductal-gray and medullary networks can inhibit or facilitate dorsal-horn processing through opioidergic, noradrenergic, serotonergic, and other mechanisms.
Sensitization changes response
Persistent inflammation or nerve injury can alter peripheral excitability, spinal processing, descending modulation, and broader network behavior.
Pain types require context
Nociceptive, neuropathic, nociplastic, visceral, acute, and chronic presentations can overlap and may require different clinical reasoning and treatment.