This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
Antagonism between acetylcholine and atropine 
Select and explain. 
A. Competitive antagonism, B. Psychological antagonism, C. Non-competitive antagonism, D. None
A: Competitive antagonism
Answer: A: Competitive antagonism 
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