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
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