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
A travelling nerve impulse does not depolarize the area immediately behind it, because 
Select and explain. 
A. It is hyperpolarized, B. It is refractory, C. It is not self propagating, D. The condition is always orthodromic
B: It is refractory
Answer: B: It is refractory 
Explanation: The area immediately behind does not depolarize because it is in a state of relative refractoriness.