What is pain of a particular part of the body? What changes in routene functioning take part?

Question

If you can give correct answer, then what is effect of pain killers on that action?

Answer 1

I guess you asking about physiological pain were nominally "painful" signals are transmitted, though they are not always perceived as painful. Although pain can be associated with tissue damage or inflammation, this is often not the case.
The experience of physiological pain can be grouped according to the source and related nociceptors. A nociceptor is a sensory receptor that sends signals that cause the perception of pain in response to potentially damaging stimulus. Nociceptors allow the organism to feel pain in response to damaging pressure, excessive heat, excessive cold and a range of chemicals, the majority of which are damaging to the tissue surrounding the nociceptor.
The regulator of pain sensation is in the CNS so I think pain killers will follow the same action as they are supposed to do..