The Nervous System

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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.
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• 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.

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Maintaining Homeostasis

• By directing the body to respond appropriately to
  the information it receives.

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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.
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On a clean page lets draw a neuron.

• Draw and color a lollipop.
• This is the cell body that contains the nucleus.

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Now, give your cell body some hair. These
extensions are called DENDRITES. The dendrites
carry impulses toward the neurons cell body.
Finally, give your cell body a nucleus.
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Your cell body needs a tail!

• The tail is called the axon. This carries
  impulses away from the cell body.

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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.
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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.

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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.