Which cranial nerve is responsible for the sense of smell?

The sense of smell is primarily mediated by Cranial Nerve I, also known as the olfactory nerve. This nerve is responsible for transmitting sensory information from the nasal cavity directly to the brain's olfactory bulb, where it is processed and interpreted as different smells. Because it has a direct role in the perception of olfactory stimuli, it is essential for the sense of smell.

Cranial Nerve II, also known as the optic nerve, is responsible for vision, relaying visual information from the retina to the brain. Cranial Nerve III, known as the oculomotor nerve, controls most of the eye's movements, as well as the constriction of the pupil and maintaining an open eyelid. Cranial Nerve IV, the trochlear nerve, is involved in the movement of the superior oblique muscle of the eye, contributing to vision but not to the sense of smell.

Thus, the knowledge that Cranial Nerve I is specifically designated for olfactory function underscores its unique role in the sensory system, making it the correct choice for identifying the cranial nerve responsible for the sense of smell.