The central nervous system consists of seven basic structures: the spinal cord, medulla oblongata, pons, cerebellum, midbrain, diencephalon and cerebral hemispheres. Each of these subdivisions are traversed by fluid-filled spaces called ventricles. A group of covers of connective tissue called meninges surrounds the central nervous system providing it protection.
As far as cell content is concerned, the central nervous system is composed of white matter and gray matter. While the white matter is predominantly made of myelinated axons that give its white appearance characteristic, gray matter contains neuronal cell bodies.
The Spinal cord emerges below brainstem and continues through the medullar canal of the spinal column. It is responsible for driving both efferent via (from the brain to the rest of the body) and afferent via (from receptor organs toward the brain).
The medulla oblongata, pons and midbrain are referred brainstem. It plays as a canal through which pass tracts that carry sensory information from the spinal cord and brainstem to the brain, but also transmit motor commands from the brain to motor neurons located in spinal cord and brainstem.
The hemispheres are formed by continuous and very folded sheets that make up the cortex. They are characterized by the presence of convolutions (crest of cortical tissue folded) and grooves (clefts that divide the convolutions each other). The combination of both creates a systematic points of reference that allows us to divide the hemispheres into lobes. The four lobes are: frontal, parietal, temporal and occipital.