The Nervous System
The nervous system receives information
about what is happening both inside and
outside your body. It also directs the way
in which your body responds to this
information. In addition, your nervous
system helps maintain homeostasis.
• Any change or
signal in the
environment that
can make an
organism react is
called a stimulus
• After your nervous
analyzes the
stimulus, it causes a
response.
• A response is what
your body does in
reaction to a
stimulus.
Maintaining Homeostasis
By directing the body to
respond appropriately
to the information it
receives.
The Neuron
The cells that carry information through your
nervous system are called neurons, or nerve
cells. The message that a neuron carries is
called a nerve impulse.
On a clean page let’s draw a neuron.
• Draw and color a lollipop.
• This is the cell body that contains the nucleus.
Now, give your
cell body some
“hair.”
These extensions
are called
DENDRITES.
The dendrites
carry impulses
toward the
neuron’s cell
body.
Finally, give your cell body a
nucleus.
Your cell body needs a tail!
• The tail is called the axon. This
carries impulses away from the
cell body.
The tips of the split tail are the
axon tips. These tips actually
“connect” to the dendrites of
another neuron to allow nerve
impulses to travel throughout
your body.
The space between the axon tip and the
dendrites is called the SNAPSE. There
is a chemical present that allows the
impulse to cross the gap between the
two nerves.
Three kinds of Neurons
• A SENSORY NEURON picks up stimuli from
the internal or external environment and converts
each stimulus into a nerve impulse.
• The impulse travels along the sensory neuron until
it reaches an INTERNEURON which carries
nerve impulses from one neuron to another.
• Some sensory neurons pass on information to a
MOTOR NEURON which sends the
information to a muscle or gland, and the muscle
or gland reacts in response.
Homework
• Read pages 626 to 630.
• Add any additional information to
your notes that you feel are
necessary.
• Define key terms page 626 in NB.