What are endorphins and how do these chemicals alter the communication of pain in the body?

Endorphins are brain chemicals known as neurotransmitters which are released when the body feels a certain amount of stress and pain. Endorphins alter the communication of pain in the body by interacting with the opiate receptors and blocking the synapse so that signals cannot be sent to the brain in order to reduce an individual perception of pain.

answer; ///i believe that the correct answer is (a) specialized cells)