Brian Is a Cross-Country Runner

Multiple Choice

Brian is a cross-country runner. He claims that he really enjoys running because he gets a wonderful "high" after running long distances. Since he knows you are taking a psychology class he asks you to explain what causes his "runner's high". You tell him that as he runs

A) serotonin blacks the pain receptors in his skin.
B) dopamine prevents his muscles from tightening up and causing pain.
C) endorphins block the chemicals that transmit pain to the brain.
D) acetylcholine is depleted in the hippocampus, blocking the formation of pain memory.