That ligand was one for which the cell had a receptor that further encouraged it to produce more of the ligand.

对于带有对应受体的细胞来说,这种配体能够刺激细胞产生更多的配体

耶鲁公开课 - 生物医学工程探索课程节选

Well, then you could imagine a cycle here where activation of the receptor is leading to production of more ligand, is leading to activation of the receptor and production of a ligand.

那么,你就能画出一个循环图,激活受体能导致,更多配体的生成,这些配体又会刺激受体生成更多配体

耶鲁公开课 - 生物医学工程探索课程节选

more excitement,more enjoyment,more passion?

寻找到更多的刺激，享受，激情？

哈佛公开课 - 幸福课课程节选