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The cerebrum is the largest part of the human brain. It is responsible for our voluntary functions and processes information from our sense organs. It develops prenatally, from the prosencephalon of the embryo. It is divided into 2 halves, the left and right hemisphere.
Humans are considered the most advanced species on the planet. We have the capacity to think, reason, apply logic, and so much more. Our emotional and logical capacity far surpasses that of other species. All the credit for this thinking ability goes to our brain, a tiny organ weighing about 3 pounds, which is what makes us so special.
Our brain is divided into 3 main parts – the cerebrum, cerebellum and brainstem. Let’s focus on the first and largest part of the brain for now – the cerebrum.
The cerebrum comprises the largest part of the brain. It develops prenatally, from the prosencephalon of the embryo. It is divided into 2 halves, the left and right hemisphere. The 2 hemispheres control opposite sides of the body, i.e., the right hemisphere controls the left side of the body and vice versa. The hemispheres are connected to each other by a structure called the corpus callosum, which is a dense, thick set of nerve fibers that divides the two hemispheres and facilitates communication between them.
The structure of the cerebrum can be studied in 2 parts – the cerebral cortex and the cerebral hemispheres.
The cortex is the outer grey matter covering the surface of the cerebrum. Each hemisphere is divided into 4 lobes. Starting from the forehead, the first lobe of the hemisphere is the frontal lobe, followed by the parietal lobe. The two are separated by the central sulcus (a sulcus is a groove or fissure). Below the frontal and parietal lobe is the temporal lobe. This is separated from the frontal lobe by the lateral sulcus. At the rear of the brain is the occipital lobe.
Grey and White Matter
The entire cerebral cortex is covered by a layer that is approximately 1/10th of an inch thick. This layer, or bark, as it is often referred to, is the place where most of our processing takes place. This layer is contains grooves and ridges, which increase the surface area. There are about 20 billion neurons and over 300 trillion synapses in the cortex alone. An increased amount of surface area, therefore, allows for more neurons to be present.
One must have heard the term “grey cells” before, especially fans of Hercule Poirot. The fictional detective often referred to them as his, “little grey friends”. These refer to the grey and white cells of our brain. The cortex is formed of neurons that lack the myelin sheath covering. The myelin sheath gives a whitish appearance to the rest of the brain. Without this, the cortex appears pinkish-grey. The grey matter is where the actual thinking and information processing is carried out. The white matter lies beneath the grey matter.
The cerebrum has many subdivisions, which control various functions. In a nutshell, the cerebrum controls all our voluntary functions, as well as our thinking, vision, hearing etc. Each of the lobes has their own specialized functions.
The frontal lobe handles our thinking, planning, short-term memory, etc. It is also a seat for most of the dopamine-delicate neurons. At the back of the frontal lobe is a section known as the motor area. This controls our voluntary actions. The left lobe also has a section called the Broca’s area, which is responsible for converting thoughts into words. Our parietal lobes control inputs like touch, temperature and taste, in addition to being responsible for our spatial balance and navigation.
Our occipital lobe receives and processes all visual information, i.e., it is responsible for all our visual activity. Any damage to this area can lead to blindness. The temporal lobe takes care of inputs that elicit memories like visual or emotional memories.
Our cerebrum controls our thinking and cognitive functions, apart from our voluntary movements. Any damage to this area can result in serious consequences, such as paralysis, blindness, loss of hearing, emotional handicap, etc. Although the cerebrum doesn’t handle functions like heart rate or body balance, it can be safe to say that our cerebrum controls many of the critical functions that differentiate us from other species.