effector

noun5

1. •
   One who or that which brings about an event or result, accomplishes a purpose, etc.

   • Yea; and I devised Numbers—high art!—and letters’ composition, / And memory, effector of all things, / And mother of the Muses: […] — 1833
2. •
   Any muscle, organ etc. that can respond to a stimulus from a nerve.
3. •
   Any small molecule that effects the function of an enzyme by binding to an allosteric site.
4. •
   An actuator.
5. •
   The part of a nerve that carries a stimulus to a muscle etc.