Your child’s sensory motor system is a very important part
of his development. In fact, almost all human activity is based in the sensory
motor system. Basically, we take in information through our senses and then we
react to it, usually with a motor response of some sort. The system is very complex and there is
coordination (it is a pre internet type of web) among all the senses and the
motor systems of the body but I will try to keep it simple here. Something
happens in the environment and the sense organs pick it up. The “sensation” is
transmitted to the brain where it is processed (and coordinated with other
information from other senses) interpreted and a response is formulated. This
information goes to the motor cortex of the brain where instructions to your
body are transmitted and you react. All this takes place in nanoseconds so your
response may seem immediate, certainly much faster than it took to read about.
Let’s use a hot iron as an example. Your finger touches the iron and the pain
and thermal sensors in your finger recognize the sensation. It is sent to the
brain which registers “HOT” and dangerous. The information is sent to the motor
areas of the brain which determines that your muscles in your arm must activate
to move your finger away from the danger. This information is sent to your
finger and you pull your finger away from the iron. Most of us have had this
experience so you know how fast this system works.
In looking at the sensory part of this system we need to
understand what the senses are. Firstly, the system consists of three basic
parts, the sensory receptor, the nerve transmitter and the part of the brain
that processes the sensation. The receptors are the organs that come in contact
with the sensation, the nerve endings throughout the body and especially around
the head that receive the sensation. The
nerves are the transport system, much like telephone cables that transmit the
sensation to the brain. All of the understanding of what was sensed takes place
in the brain. Each sense is processed in its own part of the brain separately,
although there are connections so that this information can be coordinated to
form a whole picture. This interconnection also helps when there is an
impairment in one of the senses, such as blindness, which allows information
from other senses to help “cover” for the impaired sense in gaining a better
picture of the environment.
Most of us have heard of the five senses. Many of us have
heard the term the sixth sense used to refer to unexplained abilities. Well, the truth is that we have more than 5
senses so that expression is going to have to change to the 10th
sense or something like that.
The first 4 senses are special senses, so called because they
have a single sense organ and detect a single type of sensation. These are sight, hearing, smell and
taste. Each of these has a specific
sensory receptor located around the head.
For sight it is the eyes, for hearing it is the ears. Smell and taste
are quite related and are often called the chemosenses.
The remaining senses are called the somatosenses because
they affect the body as a whole. These include touch, which is really several
senses combined under one name, the proprioceptive sense and the vestibular
sense. The first two have sense receptors spread throughout the body while the
vestibular sense uses some of the same structures in the ears that are used for
hearing.
In the next few articles, I will look at the development of
each sense both in terms of the development of the structures and of the sense
itself. Most of the sense organs develop in the absence of stimulation but
processing continues to develop with experience and, in later years , many of
the senses become weaker due to changes in the structures. After looking at
each sense in depth I would like to discuss sensory processing and the area of
sensory processing dysfunction, which is in the process of becoming a diagnosis
as well as being a symptom in several other disorders, including autism.
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