WordNet records no synonym and no antonym for olfactory bulb. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
one of two enlargements at the terminus of the olfactory nerve at the base of the brain just above the nasal cavities
Synonyms, antonyms and the broader and narrower relations for olfactory bulb come from Princeton University’s WordNet. Full sources and licences.