medulla oblongata, medulla, bulb - lower or hindmost part of the brain; continuous with spinal cord; (`bulb' is an old term for medulla oblongata); "the medulla oblongata is the most vital part of the brain because it contains centers controlling breathing and heart functioning" --4is a kind ofneural structure --4is a part of brainstem, brain-stem, brain stem --4has parts: respiratory center