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Unit 19: Biology Part 2
Conclusion
The respiratory and excretory
systems are both necessary for
life. The respiratory system takes
in oxygen-containing air and
releases carbon dioxide-containing
air. Additionally, it provides much-
needed oxygen to the organs of
the body. The excretory system
removes wastes from the body by
working together with other organ
systems. Diseases to either of
these systems can cause major
problems.
Lesson 5: Controlling
the Body
Your body is made of organs, like
your heart, lungs or stomach.
These organs work together to
allow you to breathe, eat, move,
and do just about everything else
you need to do. Organs working
together are called organ
systems. Although all organ
systems are important, and
necessary for us to survive, the
most important system might be
the nervous system, the system
that controls all the others. This
system not only controls all the
systems of your body but also
allows you to learn and use
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language, senses conditions inside
and outside your body and
prepares you to fight or flee if you
are in a dangerous situation.
Nerves and Nerve
Impulses
Imagine you walk into your home
one night and it’s pitch black. You
quickly flick on a light switch and
the room is immediately lit up.
You may have never thought about
it, but it’s kind of amazing that this
happens. Even though it may be a
long distance from the light switch
to the actual light, the light comes
on.
Fortunately, messages in your
nervous system also travel at the
speed of electricity. The nervous
system is made of bundles of nerve
cells called nerves. Nerve cells
called neurons send messages,
called nerve impulses,
throughout the body. Since these
messages are electrical impulses,
they travel very quickly. Neurons
are also covered with a fatty
covering called myelin which
insulates the neuron, like the
plastic on the outside of a wire,
allowing the nerve impulse to
travel even faster.
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