Cerebral Cortex
The cerebral cortex is a simple structure of the brain with complex functions. The neocortex, as it is called by neuroanatomists, is a thin covering of gray matter on the outer surface of the entire cerebrum. The layer is about two to three mm thick and primarily composed of two types of neurons. The surface area of the cortex of the average adult brain is around 964 in.2 (2,500 cm2). The reason for this enormous surface area compared to brain size is the result of the infolding of the surface of the brain. The hills (gyri) and valleys (sulci) that are characteristic of the brain provide the greatly increased surface. In some places the fissures or large sulci are very deep and provide a sort of map for dividing the cortex into distinct regions with specific functions.
The cortext contains about 50-100 billion neurons. There are two major neuronal types of cells distributed throughout six layers of the thin cortex. One type is the stellate cells, with round bodies and short dendrites (extensions that receive stimuli) that extend in all directions. These cells receive sensory signals and process the information in a local area. The other main cell type, the pyramidal cells, are elongate and triangular in cross-section. One end of the cell points toward the brain surface. The dendrites are thick and many are horizontal and pass into the white matter just below. They are responsible for sending signals out of the cerebrum.
There are five anatomical and functional regions in the cortex. Four are clearly visible on the surface and are named for the cranial bones that overlie them. The fifth lies deep to the lateral sulcus. It is called the insula, and its function is not yet clear. The frontal lobe is named for its place under and just behind the frontal bones and is the location for voluntary motor control, imagination, emotions, judgment, and aggressive behavior. The parietal lobe is largely responsible for integrating sensory information except hearing, smell, and vision. The occipital lobe receives and processes visual signals. The temporal lobe is a long horizontal lobe that is separated from the parietal by a long, deep, lateral sulcus. The functions are many and include hearing, learning, visual recognition (different from straight vision), and many types of emotional behavior. Memory is also a major function of this region.
The cerebral cortex covers both hemispheres of the brain and is joined by the corpus callosum. It not incorrect to say that the cerebral cortex is the main processing center of the brain. Without many of the higher brain functions associated with the cerebral cortex, many higher functions of the human brain would be impossible.
This is the complete article, containing 445 words
(approx. 1 page at 300 words per page).
