Questions: Response To Dr Foreman's Questions
a. Discuss the nociceptive mechanisms, including the postsynaptic receptors of the spinal neurons, transmitters, pathways and nuclei that are activated when the injury occurs. Also include in your answer the explanation for the sharp pain and the long lasting pain that you experience with this injury.
Nociceptors are specialized peripheral sensory neurons that are activated by noxious stimuli. These nociceptors are the free nerve endings of primary sensory neurons. Upon tissue injury, in this case the stomping on the big toe, the noxious stimuli causes tissue damage. The damaged tissues in the big toe releases a host of substances including prostaglandins, bradykinins, substance P, ATP, acetylcholine, serotonin and …show more content…
In general nociceptors are mainly unmyelinated or thinly myelinated. The nociceptors involved in the kind of pain experienced are thermal, mechanical or polymodal. Mechanical and thermal nociceptors are the peripheral endings of thinly myelinated Aδ fibers whilst polymodal nociceptors have unmyelinated C fibers. Aδ fiber axons are thinly myelinated and therefore are able to conduct action potentials faster than the C fibers. The first sharp pain (so called ‘first pain’) felt is transmitted by Aδ fibers which carry information from the damaged mechanical and thermal nociceptors. The long lasting pain(so called ‘slow dull pain’) felt is transmitted by the slower C fibers that carry signals from polymodal nociceptors. It has been shown that perception of pain results when the stimulation of nociceptors is intense enough to activate Aδ fibers leading to the initial sharp pain. With stimulus strength increase, C fibers are recruited resulting in the experience of long lasting pain which persists even when the stimulus ceases[3,