This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Magnitude of action potential is mainly affected by:September 2005 
Select and explain. 
A. Calcium ion, B. Hydrogen ion, C. Sodium ion, D. Potassium ion
C: Sodium ion
Answer: C: Sodium ion 
Explanation: Ans. C: Sodium ion