What cranial nerve is responsible for smell detection?

The correct answer is the olfactory nerve, as it is directly responsible for the sense of smell. The olfactory nerve, identified as cranial nerve 1, is unique among cranial nerves because it is not involved in any motor function or sensory modality other than smell. It consists of sensory neurons that transmit information from the olfactory epithelium in the nasal cavity to the olfactory bulb and ultimately to the brain, where the perception of smell occurs.

In contrast, the optic nerve (cranial nerve 2) is responsible for vision, carrying visual information from the retina to the brain. The oculomotor nerve (cranial nerve 3) primarily controls eye movements, pupil constriction, and maintaining an open eyelid, and does not have any relation to the sense of smell. The trigeminal nerve (cranial nerve 5) is involved in sensation from the face and motor functions such as chewing, but it does not have a role in olfaction. Understanding these distinctions clarifies how the olfactory nerve operates solely within the sensory pathway for smell detection.