Final answer:
The iris of the eye is the organ that receives both parasympathetic and sympathetic innervation, with each system influencing pupil size under different conditions.
Step-by-step explanation:
The organ that receives both parasympathetic and sympathetic innervation is c. iris of the eye. The iris controls the diameter of the pupil, which adjusts to the intensity of light. The sympathetic nervous system causes the pupil to dilate, which is useful in low-light conditions or during a 'fight or flight' response. Conversely, the parasympathetic nervous system causes the pupil to constrict, helping with high-light conditions or to focus on nearby objects.
For example, the cranial component of the parasympathetic system, which projects from the eye to part of the intestines, ends in the ciliary ganglion located in the posterior orbit. The postganglionic parasympathetic fibers then project to the smooth muscle of the iris to control pupillary size. On the other hand, the sympathetic fibers may branch throughout the body and influence the iris among other organs.