This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous System, Subject name: Physiology
Substance P is increased is response pain in periphery by which of the following? 
Select and explain. 
A. Mast cells, B. Endothelium, C. Plasma, D. Nerve terminals
D: Nerve terminals
Answer: D: Nerve terminals 
Explanation: Ans. (d) Nerve terminals(Ref: Ganong, 25th ed/p.141)Substance P#Location- primary afferent neurons in the spinal cord, nigrostriatal system, hypothalamus#Responsible for axon reflex, peristalsis, pain transmission#Receptors- neurokinin receptors (NK1 -NK3 )