We can think of the brain as a very large network of different
communication centers that can flash on and off and send messages to
one another through electrical impulses. The brain contains many
different specialized information centers scattered throughout its
three-dimensional space. These highly specialized areas of gray matter
are centers or way stations that contain the ability to remember, to
formulate decisions, and to issue commands.|
Different areas of gray matter are specialized in different functions, such as moving, seeing, touching, listening, thinking, or modulating physical functions. These specialized areas of gray matter are connected to one another through fibers that are like wires; these fiber tracks are the material that we see in the brain as white matter.
When communication between the centers in the brain breaks down, it may be due either to direct damage to a center of gray matter or to damage to the wiring between the centers. The brain has an amazing adaptive capacity that is sometimes referred to as "plasticity" - when damage occurs, messages can be sent through alternate connections.
|What part of the brain is used to feel and to regulate emotions?|
It should be of greatest interest to psychiatry. Many brain scientists
believe that the key to understanding many aspects of mental illness may
lie within the limbic system and its connections. This may be the part of
the brain that has been somehow "broken" in at least some of these patients
suffering from the schizophrenias or the affective disorders. No specific
defects in the limbic system has been uncovered as yet, but a clustering
of evidence from the study of brain chemistry and the effects of drugs
contains many tantalizing hints.
Patients with affective disorder, particularly some types of depression,
may be suffering from an imbalance in the hypothalamic-pituitary-adrenal
axis. Many of the symptoms of affective disorder are consistent with these
types of neroendocrine abnormality, since they involve changes in appetite,
sleep regulation, and adaptability to stress and change.
Organization of the brain at cellular level
The building blocks of the brain are nerve cells of two
types: neurones (10%) and glial cells (90%). At the moment, most
neuroscientists think the neurones do most of the work of the brain by
formulating and transmitting all the messages that it carries. The
glial cells are thought to be cementing, supporting, and nourishing
structures for the neurones. Some other function may be discovered for
the glial cells.
Neurones differ in shape and appearance, depending on their purpose.
Some are specialised to receive messages - the afferent( running in)
neurones or bipolar neurones. Others are specialised to send out messages
- the efferent (running out) neurones. There are also many neurones which
provide connections between afferents and efferents. These types of
cells are called "interneurons".
The main work center of the neuron is the cell body,
which contains the nucleus of the cell. The cell bodies send out tiny
fingers of branching fibers called "dendrites". This tree like web around the cell body enormously increases its ability to receive
information. In addition to the dendrites, the cell body sends out a
long tubular projection (the axon) that it uses to communicate with
other neurones. The axons are the "wires" of the nervous system, and
constitute the white matter of the brain. Different parts of the cortex
contain different kinds of neurones arranged in somewhat different
The messages are sent down the axons through a process of electrical
conduction. It is filled with a fluid containing a high concentration
of ions such as sodium, potassium, and chloride. When the electrical
impulse flowing down the axon reaches its end, it spreads out in
hundreds of nerve terminals that communicate with the dendrites and
cell bodies of many other neurones.
Many neuroscientists believe that the "break" in the brain leading to
mental illness is a breakdown in neurotransmitter systems. The
neurotransmitter system that carries norepinephrine as well as
serotonin system is important to the study of mental illness, since
there are many hints from pharmacological and neurochemical research
that patients suffering from depression may suffer from a deficit of
norepinephrine or serotonin. Although these 2 types of depression
appears to be similar in their clinical symptoms, they are due to
different chemical causes and likely to respond to different types of