Organ or Cell That Responds to External Stimulus
This page is the CodyCross answer for the clue below from Canada, Group 1264, Puzzle 2 (Five Marine Ecozones).
Question is: Organ or Cell That Responds to External Stimulus
and the answer is: RECEPTOR
Word Meaning:
RECEPTOR — (biochemistry, medicine) A protein on a cell wall that binds with specific molecules so that they can be absorbed into the cell in order to control certain functions.
Definitions from Wiktionary.