Which cranial nerve is primarily responsible for the sense of smell?

The olfactory nerve is the primary cranial nerve responsible for the sense of smell. It is the first cranial nerve and exclusively carries sensory information regarding olfactory stimuli from the nasal cavity to the brain. The olfactory receptors in the nasal epithelium detect odor molecules and send signals through the olfactory bulb, directly connecting to the olfactory cortex, which processes these signals and allows us to perceive different smells.

In contrast, the optic nerve is involved in vision, transmitting visual information from the retina to the brain; the trigeminal nerve is primarily responsible for sensation in the face and motor functions such as biting and chewing; and the facial nerve is associated with muscle movements in the face and taste sensations from the anterior two-thirds of the tongue. None of these nerves play a direct role in the sense of smell, highlighting the specialized function of the olfactory nerve in olfactory processing.