| Chapter
1
Normal Operation of the Balance System
in Daily Activities
Neil T.
Shepard, PhD
The sensation of dizziness,
whether that is a spinning of your world,
lightheaded feeling, imbalance or a combination
of these symptoms constitutes a significant
public health problem in the United States
and elsewhere. Estimates of the number
of persons in the U.S. seeking medical
care for dizziness range as high as 7
million per year. Approximately 30 percent
of the U.S. population has experienced
episodes of dizziness by age 65. There
are no indications that the problems of
dizziness and imbalance are diminishing,
particularly as the population ages. Having
an understanding of the daily function
of the balance system is important in
the comprehension of what causes symptoms
of dizziness and imbalance. This knowledge
also helps in the understanding of how
patients with these complaints are evaluated
and treated. This chapter presents information
about how the normal balance system is
supposed to function. It is intended to
support your reading of the remaining
chapters that discuss specific disorders
of balance and dizziness and techniques
for evaluation and management of those
conditions.
What
is the Balance System?
No single structure
makes up or controls balance system function.
Rather, the balance system consists of
three structures that gather information
about how we are moving, oriented to gravity
(standing on our feet or our head) and
how the world around us is moving. These
three input (sensory) structures are:
- the balance organ
portion of the inner ear, called the
vestibular endorgan (the other portion
of the inner ear is involved with hearing);
- our eyes; and
- information from
the soles of our feet and our joints
(especially the ankle, knee, hip and
neck) called proprioception.
The input information
is brought together at a level in the
back of the brain in two specific structures
called the brainstem and the cerebellum.
The input information results in routine
responses for eye movement, maintaining
upright stance and perceptions about how
you are moving.
When considering function of the balance
system, it’s helpful to look at
the major purposes that the system attempts
to accomplish. You can view these purposes
as three distinct areas:
Perceptions
of how we are oriented in a gravitational
field (standing on our feet or our head),
the direction and speed of movement and
when a change in the movement occurs.
Being able to . . . |
