Antagonism between acetylcholine and atropine
High-Yield Explanation
Ref-KDT 6/e p58 Competitive antagonists bind to receptors at the same binding site (active site) as the endogenous ligand or agonist, but without activating the receptor. Agonists and antagonists "compete" for the same binding site on the receptor. Once bound, an antagonist will block agonist binding. Ex-acetycholine and atropine antagonism