The Architecture of the Brain
Source: Adapted from "Know Your Brain", National Institute of Neurological Disorders and Stroke and the National Institutes of Health
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The Architecture of the Brain
Source: Adapted from "Know Your Brain", National Institute of Neurological Disorders and Stroke and the National Institutes of Health
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The
brain is like a committee of experts.
All the parts work together, but each part has its own special
function. The brain is shaped very
much like a giant mushroom and can be divided into three basic units: the
forebrain, the midbrain, and the hindbrain. The hindbrain includes the upper
part of the spinal cord, the brain stem, and a wrinkled ball of tissue called
the cerebellum (1). The
hindbrain controls the body=s vital functions such as respiration and heart
rate. The cerebellum is responsible
for learned rote movements like playing the piano or hitting a tennis ball. Above the hindbrain lies the midbrain
which controls some reflex actions and is part of the circuitry responsible for
voluntary movements. The
forebrain-- the cap of the mushroom--is the largest and most highly developed
part of the human brain: it consists primarily of the cerebrum (2) and
the structures hidden beneath it in the Inner Brain (see page bottom). The cerebrum is the source of
intellectual activities, holds our memories, allows you to plan, enable you to
imagine and think. The cerebrum is
divided into two halves (hemispheres) by a deep fissure. Despite the spilt, the two hemispheres
communicate with each other through a thick tract of nerve fibers that lies at
the base of this fissure. The
ability to form words seems to lie primarily in the left hemisphere, while the
right hemisphere seems to control many abstract reasoning
skills.
Each cerebral hemisphere can be divided into sections,
or lobes, each of which specializes in different functions. The two frontal lobes (3) work
together to allow you to plan a schedule, imagine the future, or use reasoned
arguments. They act as short-term
storage sites, allowing one idea to be kept in mind while other ideas are
considered. The rearmost portion of
the frontal lobe is a motor area (4), which helps control voluntary
movement. A nearby place on the
left frontal lobe called Broca=s area (5)
allows thoughts to be transformed into words.
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When you enjoy a good meal--the taste, aroma, and
texture of the food--two sections behind the frontal lobes called the
parietal lobes (6) are at work.
In front of the parietal lobes, just behind the motor areas are the
primary sensory areas (7) which are receiving information about
temperature, taste, touch and movement from the rest of body. As you look at the words and pictures on
this page, two areas at the back of the brain are at work. These lobes, called the occipital
lobes (8), process images from the eyes and link that information with
images stored in memory. The
temporal lobes (9) which nest under the parietal and frontal lobes are
active when you are listening. The
upper portion of the temporal lobes receives information from your ears and the
underside plays a crucial role in forming and retrieving memories, including
those associated with music. Other
parts seem to integrate memories and sensations of taste, sound, sight, and
touch. Coating the surface of the
cerebrum and the cerebellum is a vital layer of tissue the thickness of a stack
of two or three dimes. This thin
rind is called the cerebral cortex, commonly referred to as the Agray matter,@ and is where most of the actual information processing
in the brain takes place.
Deep within the brain lie structures that are the
gatekeepers between the spinal cord and the cerebral hemispheres. These structures determine our emotional
state, modify our perceptions and responses depending on that state, and allow
us to initiate movements without thinking about them. The hypothalamus (10), about the
size of a pearl, directs a multitude of functions including waking you in the
morning, and getting the adrenalin flowing during a test or job interview. The hypothalamus is also an important
emotional center, controlling the molecules that make you feel exhilarated,
angry, or unhappy. Near the
hypothalamus lies the thalamus (11) which is a clearinghouse for
information going to and from the spinal cord and the cerebrum. An arching tract of nerve cells leads
from the hypothalamus and the thalamus to the hippocampus (12), a tiny
nub acts as a memory indexer--sending memories out to the appropriate part of
the cerebral hemisphere for long-term storage and retrieving them when
necessary. The basal ganglion
(not shown) are clusters of nerve cells surrounding the thalamus which are
responsible for initiating and integrating movements.
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The
brain is made up of many types of cells, but the primary functional cells are
called neurons. All sensations,
thought, memories, and feelings are the result of signals that pass through
neurons. Neurons consist of three
parts. The cell body (13)
contains the nucleus, where most of the molecules that the neuron needs to
survive and function are manufactured.
Dendrites (14) extend out from the cell body like the
branches of a tree and receive messages from other nerve cells. Signals then travel down the axon
(15) to another neuron, a muscle cell, or cells in some other organ. The axon is wrapped by other cells which
form a sheath (16) which provides insulation for the axon and helps nerve
signals travel faster and farther.
The
place where a signal passed from one neuron to another cell is call the
synapse. When a signal reaches the
end of the axon it stimulates tiny sacs (17) which release chemicals
known as neurotransmitters (18) into the synapse (19). The
neurotransmitters cross the synapse and attach to receptors (20) on the
receiving cell. If the receiving
cell is also an neuron, the transmission of the signal continues to the next
cell.
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For more information about Mental
Illnesses
Contact:
The Alliance for the Mentally Ill
NAMI of Greater Chicago
1536 West Chicago Ave, Chicago, IL
60622
Phone: 312-563-0445