BRAIN, DRAWING. BRAIN, DRAWING Model. The brain is composed to two hemispheres which are joined in the center by nerve fibers composing the corpus callosum. Together with the brain stem and the cerebellum which extends posteriorly, these structures compose the encephalon or brain. The surface of the hemisphere are molded into a number of irregular eminences called gyri or convolutions separated by furrows termed sulci or fissures delimiting lobes. The lobes of the brain (frontal, parietal,