Which cranial nerve is responsible for the sense of smell?

The sense of smell is primarily mediated by the olfactory nerve, which is also known as cranial nerve I. This nerve has specialized sensory receptors located in the nasal cavity that detect odor molecules. Once these receptors are activated, they send signals through the olfactory nerve directly to the olfactory bulb in the brain, which processes the information related to smell.

The other choices involve different functions: the optic nerve is responsible for vision, the oculomotor nerve controls eye movements and pupil response, and the trigeminal nerve is primarily concerned with sensation in the face and motor functions such as biting and chewing. None of these nerves serve a direct role in olfaction, which is uniquely attributed to the olfactory nerve. Understanding the distinct roles of cranial nerves is essential for recognizing their specific sensory and motor functions in the nervous system.