The How the Brain works.

HOW THE BRAIN WORKS
PART II

THE LONGEST LIST OF THE LONGEST STUFF AT THE LONGEST DOMAIN NAME AT LONG LAST

How does the brain work?



The cerebrum is the largest part of the brain and there are many different parts to it. The cortex covers most of the external portion of the brain. The total area of the brain is approximately 233 to 465 square inches. To be able to fit inside the skull, the cortex is divided into many folds and grooves. The folds are called gyri and the grooves are called sulci. It is the large pieces of the sulci that divide the brain into different lobes. These are the frontal lobe, parietal lobe, occipital lobe, and temporal lobe. Each of these lobes as well are responsible for different functions.

The largest groove is the interhemispheric fissure and this divides the brain into right and left hemispheres. The two different hemispheres communicate to each other using fibers that are called corpus callosum. The right and left temporal lobes also use fibers to communicate with each other. These fibers are called anterior commisure and these fibers are located near the back of the brain. The area of the cortex above the corpus callosum is divided by another groove called the cingulate sulcus. This is also sometimes referred to as the limbic system or the limbic lobe. The basal ganglia, amygdala, and hippocampus are all buried deep inside the cerebrum. Those are the major parts of the cortex and they all have different roles to play.

The parietal lobe controls the processing of information when it pertains to somatosensory input from the different areas of the body. These areas can be senses such as touch and pain. The spinal cord contains fibers that carry from the thamalus to the parietal lobe. The different connections all form one unit that is displayed as a sort of graph of the human body on the parietal lobe. That graph is referred to as the homunculus. On the graph, each area to receive sensory input is displayed in relation to the amount of sensory input it can receive, and not the actual size of the area. The hands are very big, as they receive much sensory input and are much bigger on the graph than any other area of the body. To the back of the parietal lobe is the Wernicke’s Area. This portion of the lobe is responsible for correctly interpreting language. When this area of the brain is compromised, a person will not be able to understand language but they will still be able to make sounds.

The frontal lobe plays a major part in motor skills and cognitive functions. The motor centre of the brain is placed in the back of the frontal lobe and lies before the parietal lobe. It takes connections from the somatosensory part of the parietal lobe and begins motor functions. Just like the graph of the human body in the parietal lobe, the frontal lobe has a graph of the motor functions of the brain. Broca’s Area is located at the front of the frontal lobe and controls the muscles that are responsible for making sounds such as the lips, larynx, and tongue. If this area is compromised, the opposite effect takes place from that of the Wernicke’s Area. In this case, someone will be able to understand language but will not be able to make any sounds. The rest of the frontal lobe is responsible for other processes such as thought, learning, and memory.

The occipital lobe takes information from the eyes and passes this information along to the Wernicke’s Area and the motor portion of the frontal lobe. When objects are seen upside-down in the retina, it is the occipital lobe that translates them into right side-up. The temporal lobe is responsible for receiving auditory messages from the ears and taking it to the Wernicke’s Area and the motor portion of the frontal lobe. The insula controls the automatic activity in the brain stem. The insula also receives and analyzes messages relating to taste.

The hippocampus is held within the temporal lobe and is involved mainly with short-term memory functions. The amygdala is also located within the temporal lobe and its main function is to command behavior and sexual functions. The limbic system plays a large role in the control of different movements and different behaviors that are related to emotions. Another portion of the human brain is the basal ganglia and that also plays an important role in movements. It is mainly concerned with fine motor movements, such as wiggling the fingertips.

Finally, all of the grooves and folds that make up the brain are encased in a number of membranes that are called meninges. These membranes protect the brain from coming into contact with the skull and the spinal cord. The skull and the spinal cord are also encased in cerebrospinal fluid, to provide further protection from harm. The choroid plexus tissue creates this fluid. These tissues are held inside the brain and when the fluid is created, it flows through the brain, through the cavities, and down the spinal cord, covering everything in its path. There is a blood-brain barrier to prevent this fluid from entering the bloodstream.

The human brain is a very complex organ. With as much information as this is, it is really only the basic functions and parts of the brain that are comprised to make it whole. It is easy to see however, how each area of the brain is extremely important for the brain to be able to function properly and how when one area of the brain is compromised in any way, it can easily affect the entire organ.

PART I

the Brain.

 The How the Brain works of the Brain.

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