Which of the following is a cranial nerve that carries the sense of smell?

• A. Olfactory
• B. Optic
• C. Trigeminal
• D. Vagus

Answer: (A)

Smell relies on a single cranial nerve dedicated to olfaction, carrying sensory information from the nasal cavity to the brain. Odor molecules bind to receptors in the nasal epithelium, and the resulting signals travel along olfactory nerve fibers through the cribriform plate to the olfactory bulb, then onward to brain regions that interpret smells. This nerve is purely sensory for smell. The optic nerve handles vision, the trigeminal nerve mainly conveys facial sensation and chewing movements (and can sense irritation in the nose, but it does not detect odors), and the vagus nerve supplies autonomic and visceral functions. Therefore, the nerve responsible for the sense of smell is the olfactory nerve.