Researchers using PET scans to study the opioid system in long-distance runners are likely to find increased brain levels of _____ following a long run.
A) acetylcholine
B) endorphins
C) GABA
D) cerebrospinal fluid

Question

Quizplus · Accepted Answer

The opioid system is known to be involved in the release of endorphins, natural chemicals produced by the body that have pain-relieving and euphoric effects. Long-distance runners have been found to experience an increase in endorphin levels during and after a run, which is likely to be detected by PET scans of their brain activity.

Researchers Using PET Scans to Study the Opioid System in Long-Distance