effector
noun [ C ] biology specialized uk/ɪˈfek.tər/ us/əˈfek.tɚ/
效应器，效应物（机体中对刺激做出反应的组织、器官或物质）
a body part or cell that reacts to a stimulus in a particular way, or a cell or substance in the body that produces an effect
effector cells 效应细胞
In a reflex, the effector muscle acts before your brain is able to think. 在做反射动作时，效应肌肉在大脑意识之前就做出反应。