Be aware that underneath these situations there could be pain either without any stimulus or with an incredibly gentle, non-tissue-harmful stimulus. Absolutely nothing is known about how these stimuli activate nociceptors. The nociceptive nerve endings are so tiny and scattered that they're tricky to discover, not to mention examine. https://nanobookmarking.com/story18110944/new-step-by-step-map-for-what-are-pain-receptors