The cerebrum is based in two complex hemispheres segregated into five paired lobes. Responsible for higher brain function, which includes the interpretation and reception of the nerve impulses, initiating voluntary movement, memory, thought processes, and logical reasoning, the cerebrum is also highly involved in emotional response and instinctual response.


The cerebrum is easy to recognize as it is the largest and most obvious section of the human brain. Located in the telencephalon region, the cerebrum takes up about 80% of the brain’s mass.

A longitudinal fissure segregates the right cerebrum hemisphere from the left. A large tract of white brain matter is responsible for internal connection. This white brain matter is known as the corpus collosum. Extending into the longitudinal fissure which segregates the two hemispheres, the falx cerebri is a relative connection of the menenges.

Each individual hemisphere is equipped with a central cavity which is known as the lateral ventricle and is lined with epindymal cells. These cavities are also filled with cerebral spinal fluid. Two distinct layers comprise the cerebrum. The cerebral cortex is the outer layer created by gray matter of 2 to 4 millimeters in thickness. Just below the gray matter surface is the white matter layer. Convolutions, the vast complex array of folds and wrinkles along the brains surface, are formed during the development of a fetus. During this developmental stage, the brain size is known to increase at an alarming rate and the gray matter cortex outgrows the underlying white matter, leaving the folds and wrinkles on the brain’s surface.


Image: Cerebrum

The folds which are elevated from the brain’s surface are called the cerebral gyri. The grooves created by these folds are alternatively called the cerebral sulci. The overgrowth of the gray matter of the brain during fetal development effectively increases the surface area of the brain to three times the size it would otherwise be. These additional folds are then laden with nerve cell bodies.


The cerebrum is first divided in half, each considered a lobe. From there, each lobe is then again divided creating five lobes on each hemisphere. Fissures create the subdivisions, four of which are found on the cerebrum’s surface. Each subdivided lobe is named for the cranial area, particularly the bone, which is responsible for its protection. The divisions are each responsible for their own specific function.


Cerebrum Lobes
Image: Cerebrum Lobes


The frontal lobe can be found in the foremost section of the brain, on each hemisphere. Segregating the frontal lobe from the parietal lobe is a deep furrowing fissure known as the central sulcus, or alternatively the fissure of Rolando. Extending out at right angles from the longitudinal fissure, it meets with the lateral sulcus. The lateral sulcus in alternatively named the fissure of Sylvius, and protrudes laterally to segregate the frontal lobes from the temporal lobes. Just in front of the central sulcus, the precentral gyrus is responsible for vast amounts of motor skills. The frontal lobe is vital in performing functions such as large motor skills and skeletal movement, developing personality, and providing analysis of sensory experiences. Its secondary responsibilities include mediating the responses to judgment, planning, reasoning, memory, emotions, and verbal communications.


Behind the central lobe, just posterior to the central sulcus, one finds the parietal lobe. Immediately posterior to the central sulcus lies the postcentral gyrus, which is a major contributing area for sensory development and interpretation. This area is vital for response to stimuli pertaining to coetaneous and muscle receptors throughout the entire body. The postcentral sulcus is a somatesthetic area. The precentral gyrus and the postcentral gyrus are not appropriately sized in relation to the areas they serve. The precentral gyrus, which is responsible for motor movement, and the postcentral gyrus, which is responsible for sensory stimulation response, corresponds in size to the number of motor units or the density of the receptors.

This is more adequately explained when looking at a specific body part, such as the hand. The hand is equipped with a large number of motor units as well as a high density of receptors. The portions of the precentral and postcentral gyri that serve the hand are larger than those that serve the thorax despite the fact that the thorax is much larger than a hand. The hand is more complex in regards to the central nervous system and this requires a larger gyrus devotion.

The parietal lobe is not only responsible for somatesthetic stimulation response, but it is also largely responsible for understanding language and evolving thoughts as well as emotions. It also is responsible for determing things such as shape, texture, and feel of object when they are handled.


The temporal lobe, which is positioned under the parietal lobe and behind the frontal lobe, is segregated from these bordering lobes via the lateral sulcus. The temporal lobe, via sensory fibers which are received from the cochlea of the ear, is responsible for interpreting and receiving sound. Part of the function of the temporal lobe is memory recording of a percentage of visual and auditory experience as well as the interpretation of other sensory experiences.


The occipital lobe blends in with the neighboring lobes, the temporal and the parietal lobes. It forms the posterior segment of the cerebrum. Positioned inferior to the cerebellum, it can be distinguished from this lobe via a folded portion of the meningeal layer. This layer is known as the tentorium cerebelli. The occipital lobe is responsible for vision related sensory function. This lobe directs the eye as well as focuses it on the line of sight. Taking it one step farther, it also correlates the eyes’ experiences with previous visually related functions, such as sight recognition.


The insula is a buried lobe which can not be found when looking at the outside of the brain. Scientific study has not yet been able to completely determine the significance of the insula, however, it is known to have the power to integrate the activities of the other lobes. Under the parietal lobe, the occipital lobe, and the frontal lobe, the mysteries of the insula have yet to be fully discovered.
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