What does the brain do?
The brain controls and co-ordinates
everything we do. Its purpose is to receive messages,
process those messages and respond to them. The responses
generated by the brain allow us to think, move, breathe,
speak, show emotion and regulate all of our other
bodily functions.
The brain forms a part of our central
nervous system. It is soft jelly-like substance weighing
about three pounds on average and sits inside the
skull, cushioned by a liquid known as cerebrospinal
fluid. Although the brain only accounts for two percent
of body weight, it uses twenty percent of the body’s
oxygen supply and blood flow.
What is it made of?
The brain is made of billions
of brain cells. Some cells, known as neurons are
responsible for carrying messages to and from the
brain. Other cells, known as glia provided the support
structure for the neurons.
Neurons require oxygen to function,
and begin to die within about 3 to 5 minutes without
it. The neurons themselves are quite fragile and
need extensive protection from being crushed, infected
or other harm. The long fibrous parts of neurons,
called axons are prone to tearing when sudden movements
such as those that occur during a car accident injure
the brain. This can result in a form of injury known
as diffuse axonal injury.
Protective Layers
There are several layers of tissue
that protect the brain. Beneath the skin of your
scalp is bone (your skull). Below the skull are three
special coverings called the meninges. Meningitis
is an infection of the meninges. The out later of
the meninges is called the dura. This is a tough
layer, which restricts the movement of the brain within
the skull and so protects it from damage. Bleeding
below this layer can result in a subdural
haematoma. Bleeding above the dura can result
in an extradural haematoma. This
middle layer of the meninges is called the arachnoid.
A bleed that occurs in the space between this layer
and the next is a subarachnoid hemorrhage.
The inner layer, the one closest to the brain, is
called the pia mater.
Internal Structure of
the Brain
Over the course of its long evolution
the brain had developed three major parts: 1.) The
cerebral cortex, or the cerebrum is the large mass
of tissue shaped like a wrinkled walnut. 2.) The
cerebellum is the fist-like structure located at
the rear and base of the brain and, 3.) The brain
stem is the lowest (and oldest in evolutionary terms)
part of the brain connected to the spinal cord. The
cerebral cortex is divided into two halves or hemispheres.
The two hemispheres transfer information through
a bridge of nerve fibers called the corpus callosum.
The left hemisphere controls the
right side of the body. For most people the left
hemisphere is involved in the understanding and expression
of language. The right hemisphere controls the left
side of the body, and is involved in spatial and
artistic skills.
Each half, or hemisphere of the
cerebrum is divided into four areas known as lobes.
The four lobes are: 1.) Frontal Lobe, 2.) Parietal
Lobe, 3.) Temporal Lobe and 4.) Occipital Lobe.
What does each part do?
Lobes of the Cerebrum
The frontal lobe is
located behind the forehead and is involved in
task such as reasoning, planning, problem solving
and organizing along with acting as a control for
personality, behaviours and emotions. Marked changes
in a person’s personality and social skills
can occur from damage to this area. The motor cortex
at the back of the frontal lobes controls movement.
The parietal lobe controls
the sense of touch including pressure, temperature
and pain. It is involved in fine motor movements,
arithmetic and spelling. At the front of the parietal
lobe is the sensory cortex in the frontal lobe.
This controls our perception and how we interpret
sensation and movement.
The temporal lobe is
involved in receiving and processing auditory information
e.g. music and speech and plays a major role in
memory storage and learning.
The occipital lobe is
situated at the back of the head and is instrumental
in controlling the sense of sight.
The Cerebellum
The cerebellum helps to regulate
balance and co-ordination. It provides a “feedback
mechanism” to adjust muscle activity so that
balance is maintained. It also plays a role in regulating
muscle tone.
The brain stem
The brain stem comprising of the
pons and medulla oblongata regulates essential life
functions such as breathing, heart rate and blood
pressure. It also serves as a “rely station” for
messages regarding movement and sensation. Cranial
nerves are located in the brain stem, which regulate
a number of functions such as swallowing, speech
and eye movement.
The limbic system
The limbic system, which is sometimes
known as the “emotional brain,” is found
buried within the cerebrum near the temporal lobe
and is made up of the thalamus, hypothalamus, amygdale
and hippocampus.
This system deals with sensory
information such as vision, controls hunger and
thirst. It also plays a role in emotions such as
fear and is essential in memory and the process
of memory retrieval and learning.
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