any of the 12 paired nerves that arise from the lower surface of the brain with one of each pair on each side passing through openings in the skull to the periphery of the body; olfactory (I), optic (II), oculomotor (III), trochlear (IV), trigeminal (V)—including ophthalmic (V1), maxillary (V2), and mandibular (V3)— abducens (VI), facial (VII), vestibulocochlear (VIII), glossopharyngeal (IX), and vagus (X)