Nerve Fibers (image) McGill University Caption Sympathetic nerve fibers (depicted in red) are shown to wrap around the pain-sensing neurons (green) in the joint synovium of arthritic animals. Credit Geraldine Longo, McGill University Usage Restrictions One-time use only. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.