In response to harmful stimulus, nociceptors initiate neural impulses leading to sensation of pain. Nociceptors are receptors located at the end of a sensory neuron's axon. They respond to potentially damaging things by sending a signal to the spinal cord and brain that lets it know that there is a possible thread. If the brain believes the threat is real it will create a painful sensation at the body part in danger to alert the body and save itself from the threat.
