Pupil fails to dilate by giving cocaine in :

Ans. is 'd' peripheral sympathetic paralysis 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:1. Mydriasis2. Rise in B.P.3. Local vasoconstriction4. TachycardiaTherefore if the peripheral sympathetic system is paralysed it will lead to reverse of the above mentioned actions.