In general, pain receptors are classified according to their location (Carey, 1985). Receptors that respond to injury or noxious stimuli are termed nociceptors and are sensitive to thermal (heat), electrical, mechanical, chemical and painful stimuli. Each nociceptor is connected to a nerve that
transmits an electrical impulse along its length towards the spinal cord and then, ultimately your brain. It is your brain that informs you whether or not you are experiencing pain. (Hoskins and Welchew 1985).
Pain Messages Travel Slower than Other Nerve Stimulation
Nerves can also be categorized according to their diameter (width) and whether or not a myelin sheath is present.
Fordham (1986) suggested that three types of nerves are concerned with the transmission of pain.
- A beta fibres, which have a large diameter and are myelinated.
- A delta fibres, which have a small diameter and also have myelinated sheaths.
- C fibres, which have small diameters and are non-myelinated (slowing their conduction rate) and are generally involved with the transmission of dull, aching sensations (Carey 1985). Nerves with a large diameter conduct impulses faster than those with a small diameter (Hoskins and Welchew 1985). The presence of a myelin sheath also speeds up the nerve conduction rate.