Pain Receptors Within the Human Nervous System

What pain receptors do humans have within the nervous system?

Discuss different types of nociceptors, mechanical, chemical, thermal, and polymodal. Which body parts are more sensitive to pain and which are not? Discuss why some people have a higher tolerance to pain and what is associated with it. Further on, discuss the three types of opioid receptors that regulate pain signals, mu, delta, and kappa opioid receptors. Also, discuss pain medication and how it works chemically with our body to ease the pain.