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It is always a pleasure to see circus acrobats walk the
tight-rope with such agility and style. But in reality, all of us do our kind of balancing
act. Every second of the day we make sure that our head and the rest of our body
are in an upright position. During the first two years of life, we learn how to work
against the force of gravity, which is constantly operating on us. One of the organs that
help us maintain our balance is the ear. Normally we only associate the ear with hearing
or sound, but it is responsible for monitoring every little movement of the head. If
accurate monitoring takes place, then in case of imbalance, the body can adjust itself and
come back to normal.
The delicate organs of balance are located in the innermost part of the ear or the inner
ear, which is properly protected by the skull bones. This inner ear consists of a
maze of tubes filled with fluid to different levels and positioned at different angles. The
three main ones that are directly connected to balance are the utricle, the saccule and
the semi-circular canals. |
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The function of the utricle and the saccule is to detect the position of the head.
Both these two cavities contain a pad of cells, laid with a jelly-like substance, which in
turn has small granules of chalk embedded inside. When the body is straight, the
gravitational force makes these granules press against sensitive hairs in the jelly. The
hairs then send nerve signals to the brain that tell it, 'upright'.
When the head leans front, back or sideways, the chalk granules push against the hairs,
and bend them in a different direction. This sends off new messages to the brain, which
can then, if needed, send out instructions to the muscles to immediately adjust the
position of the body.
The utricle is also springs into action when the body starts to move forwards or
backwards. If a child, for example, begins to run, the chalk granules get pushed back
against the hairs, which makes it seem as if the child were falling backwards. As soon as
the brain receives this information it sends out signals to the muscles; this makes the
body lean forwards thus restoring its balance.
When the body moves,
the endolymph fluid in the semicircular canals causes the hairs in the galatinous mass
to bend. These are connected to the vestibular nerve, which alerts the brain
to re-balance the body.
When the body halts or begins to move
Spreading out just above the utricle of the ear, we have three fluid-filled
semicircular canals. The base of each canal has an oval mass of jelly, which
encases the tips of sensitive hairs. These hairs bend as a result of movements of fluid in
the canals, which occurs when the head moves.
The semi-circular canals immediately get the information when the head starts and stops
moving - especially during quick, intricate movements. When the head begins to move one
way, the fluid in the canals tends to stay still, thus making it push against the
sensitive hairs. The hairs then send messages to the brain, which takes necessary action.
But when the head stops moving, in particular when it stops turning round and round, the
fluid continues to move inside the semi-circular canals for up to a minute or more; this
causes dizziness.
Centre of Control
As said earlier, the ear is only one of the organs that is involved in balancing, the
other important ones being the cerebellum (this part of the brain has the
duty of directing the action of the muscles) and the eyes - these provide
vital information about the body's position in relation to the surroundings and
secondly, the eyes are also linked to the semi-circular canals. For instance,
when the head begins to move to the left, the fluid movement in the semi-circular canals
causes the eyes to move to the right. But the balance mechanism soon makes them move to
the left so as to adjust to the head's position. This partly explains why people are more
likely to be become sick if they try to read while traveling in a moving vehicle, such as
a car or bus. The reading tends to counteract these natural eye movements and sadly
triggers off feelings of nausea and vomiting.
We all learn how to balance our head and body when we are hardly two years of age - it is
quite an achievement since the muscles, eyes and brain have to work in harmony.
Tight-rope walkers move on ahead to achieve greater control over their body and make good
use of this power of balancing!
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