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: Anaesthesia
Pupil fails to dilate by giving cocaine in – 
Select and explain. 
A. Central sympathetic paralysis, B. Central parasympathetic paralysis, C. Peripheral parasympathetic paralysis, D. Peripheral sympathetic paralysis.
D: Peripheral sympathetic paralysis.
Answer: D: Peripheral sympathetic paralysis. 
Explanation: In periphery cocaine blocks the uptake of Adrenaline and Noradrenaline in Adrenergic nerve ending resulting in higher concentration of sympathetic neurotransmitters (Sympathomimetic effect) :
The peripheral sympathomimetic action of cocaine produces following effect :


Mydriasis
Rise in B.P.
Local vasoconstriction
Tachycardia


Therefore if the peripheral sympathetic system is paralysed it will lead to reverse of the above mentioned actions.