The cerebrum is definitely the most complex organ of the whole human body. Perhaps the most interesting characteristic is that, despite its size (about 9 times bigger than the cerebellum), it has an equal amount of neuronal cells.
Basically, the cerebrum is physically divided in two hemispheres (the cerebral cortex), but comprises as well the basal ganglia and the limbic system. Both of the hemispheres (they are separated, but are still linked together by the corpus callosum, that is a thick band of nerve cells responsible for transferring motor and sensitive information) are divided into four lobes:
- the frontal (which is responsible for the motor functions);
- the parietal (the most important sensitive center in the body);
- the occipital (involved in vision);
- the parietal lobe (responsible for the hearing and for the olfaction ability).
In terms of structure, the upper part of the cerebrum, called the cerebral cortex, comprises 6 dense but thin layers of neuronal cells. As well, by simply viewing a cerebrum, anyone can tells that it has lots of convolutions, that in turn, have gyry (plural for gyrus) and sulci (plural for sulcus; are fissures or depressions in the brain’s outermost space and on the surface).
The basal ganglia is not a singular structure at all. In fact, it’s often referred to as a group of nuclei in the cerebrum connected to most of the important relay structures in the brain such as the thalamus and other parts. They are responsible for creating habits, for the voluntary motor control, but also for the cognitive and the emotional processes.
Last, but not least, the limbic system comprises several structures responsible especially for the control of the emotions, the behavior, the processes of learning and especially for memorizing things for the long term. The limbic system is also called the paleomammalian brain and comprises the amygdala, the fornix, the septal nuclei, fornix and the dentate gyrus asides many other. Some scientists say that without them, the humanity as we know it, would not have evolved too much from the Stone Age.