What physiological effect does sympathetic stimulation exert on the human eye pupil?
Answer and explanation
Correct answer: D. Mydriasis via contraction of the pupillary dilator muscle
Sympathetic postganglionic fibers from the superior cervical ganglion release norepinephrine onto alpha-1 adrenergic receptors of the radial pupillary dilator muscle, causing pupillary dilation (mydriasis). Parasympathetic fibers cause pupillary constriction (miosis).
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