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Unit 19: Biology Part 2
the cerebellum. The brain stem is
concerned with basic functions of
the body that we don’t even have
to think about doing. These
activities include such important
activities as digestion, heartbeats,
and even breathing.
Figure 52 – The cerebellum and
brainstem lie under the
cerebrum, which is divided into
four lobes.
The other organ of the CNS is the
spinal cord. The spinal cord is a
long, tube-shaped bundle of
neurons. Running from the
brainstem to the lower back, the
spinal cord is like the highway of
the nervous system. Messages get
sent from the parts of the body to
the brain, providing the brain with
critical information about the inside
and outside surroundings. The
brain sends back messages telling
the parts of the body what to do
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based on the information it was
given. All this information is sent
in the form of nerve impulses up
and down the spinal cord.
Figure 53 – The spinal cord
runs from the brainstem to the
lower back.
Peripheral Nervous System
The nervous system is not just
made of your brain and spinal cord.
From your arms and hands, down
to your feet and legs, up to your
scalp and face, and even to the
organs inside you, all your body
parts have nerves traveling to and
from them, so that messages can
get to the CNS. This network of
nerve cells outside the CNS is
called the peripheral nervous
system (PNS.) The nerves of the
PNS are connected, either directly
or indirectly, to the spinal cord.
Within the PNS is two divisions, the
sensory division and the motor
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