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The question might seem weird. Does sympathetic nervous system acts 'bilaterally' meaning if you shout to a person's left ear a loud noise (e.g. by headphones), will it activate sympathetic system just on the left or on the both sides. For example it will only dilate left pupil or dilate both ?

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Yes, they do. At least in the case of pupils. In fact, the absense of simultaneous regulation of the diameter of the pupil is used as a medical test for the evaluation of brain damage.

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