Nociceptors

Nociceptors are sensory cells specialised in the perception of noxious stimuli. They perceive mechanical, thermal and chemical stimuli. They are free nerveenendings.

The pain signal is then transmitted over long axons through the spinal nerves into the rear horns of the spinal cord, where the nociceptors form their synapse. The spinal cord neurons that follow then run via the thalamus into the brain, where the pain is perceived. The cell bodies of the nociceptors lie in the spinal ganglia near the spinal cord. Each ganglion contains the cell bodies of several thousand sensory neurons - most of them pain cells. The diameters of the neurons vary between 20 µm and about 50 µm, the diameter of the ganglion is about 2 mm.