end organ

/EH1 N D AO1 R G AH0 N/
noun
  1. 1

    A small organ at the terminal end of a nerve conduction pathway.

  2. 2

    The ultimately affected organ in a chain of events, such as a disease process (pathophysiology) or a drug's mechanism of action (sometimes called a target organ in this sense).

Source: https://en.wiktionary.org/wiki/end%20organ