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
Conduction along membrane is dependent on all of the following EXCEPT: March 2013 
Select and explain. 
A. Ca2+, B. K+, C. Fe2+, D. Na+
C: Fe2+
Answer: C: Fe2+ 
Explanation: Ans. C i.e. Fe2+ A decrease in extracellular Ca2+ concentration increases the excitability of nerve and muscle cells by decreasing the amount of depolarization necessary to initiate the changes in the Na+ and K+ conductance that produce the action potential. Conversely, an increase in extracellular Ca2+ concentration can stabilize the membrane by decreasing excitability.