Transmission 1 - nociceptor to spinal cord

Once a nociceptor has been stimulated an electrical signal, or action potential, is generated and this travels via sensory neurones to the spinal cord. Two main types of neurones are involved. C-fibres are small, non myelinated axons that conduct slowly at about 2m per second. A-delta fibres have a greater diameter and are myelinated. Consequently they conduct impulses more rapidly at 5-30m per second.

A-delta fibres tend to transmit acute, well localised, sharp pain, whereas C-fibres tend to transmit more diffuse aching type sensations.

Think about what happens when you stub your toe. The first sensation is a sharp pain that makes you grab your foot. This is transmitted by the fast A-delta fibres. Then comes the long dull throbbing sensation – transmitted by the slower C-fibres.