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Science.7
The Nervous System
Essential Questions
1. How does structure and functions between and
within systems maintain life in an organism?
2. How does the nervous system sense and respond
the stimuli in the environment?
Vocabulary
nervous system, brain, spinal
cord, neuron, nerves
Name ______________________________
Date _______________________________
Objectives
1. Identify the structures in the nervous system
2. Identify the function of the nervous system.
3. Describe how the nervous system senses and responds to
stimuli in the environment.
Text adapted from EdHelper and http://yucky.discovery.com/flash/body/pg000136.html
Tasting, smelling, seeing, hearing, thinking, dreaming, breathing, heart beating, moving, running, sleeping,
laughing, singing, remembering, feeling pain or pleasure, painting, writing...you couldn't do any of these things
without your nervous system!
What is the function of the nervous system?
Your nervous system is the control and
communication system of the body. Its job is to send
and receive messages, controls all your thoughts and
movements. It allows you to respond to changes in the
environment. Your nervous system also controls all the
other organ systems in your body and works with your
endocrine system to maintain stability, or homeostasis,
within your body. Without it, you couldn't exist!
What are the structures of the nervous system?
Of all the body systems, the nervous system is
the most complex. It is made up of your brain, your
spinal cord, and an enormous network of nerves that
thread throughout your body.
The Brain
The brain is the command center of your entire body. The brain is the body's main information center.
It is made of billions of neurons and sends and receives electrical signals through the spinal cord. The brain
helps the body respond to the information it receives from the senses. The brain also processes thoughts.
When you think, neurons in your brain are working. The brain is linked to the spinal cord by the brain stem.
The brain stem controls digestion, breathing and your heartbeat.
The Spinal Cord
The spinal cord is like a major freeway. The spinal cord is a tube of neurons that runs up the spine and
attaches to the brain stem. All signals to and from the brain travel past the spinal cord. Information from
nerves that branch out to the rest of the body goes to the spinal cord. Some messages are processed by the
spinal cord but most information is sent on to the brain.
What are the cells within the nervous system called?
The cells that make up the nervous system are called neurons. Long, stringy neurons are perfect for
carrying the electrical messages that are the "language" of the nervous system.
What are nerves?
They're the thin threads of nerve cells, called neurons that run throughout your body. Bundled
together, they carry messages back and forth just the way that telephone wires do. Sensory nerves send
messages to the brain and generally connect to the brain through the spinal cord inside your backbone. Motor
nerves carry messages back from the brain to all the muscles and glands in your body.
So how do they pass along messages?
Through the marvels of chemistry and a kind of electricity! Neurons are thin. Some are very small, and
some can be three feet long! All are shaped somewhat like flat stars which have, to varying degrees, been
pulled at each end so that they have long fingers. The fingers of one neuron almost reach to the next neuron.
When a neuron is stimulated -- by heat, cold, touch, sound vibrations or some other message -- it
begins to actually generate a tiny electrical pulse. This electricity and chemical change travels the full length of
the neuron. But when it gets to the end of finger-like points at the end of the neuron, it needs help getting
across to the next extended finger. That's where chemicals come in. The electrical pulse in the cells triggers
the release of chemicals that carry the pulse to the next cell. And so on and so on and so on.
Remind you of anything?
How about a cool relay of dominoes in which one standing domino
falls and trips the next, and the next, and the next?
QuickTime™ and a
decompressor
are needed to see this picture.
Why Do I Shiver When I Am Cold?
The body always works at keeping its temperature at a constant level. You probably know that this
temperature is 98.6 degrees F. At this temperature the cells of the body work best. One of the jobs of the
nervous system is to maintain homeostasis, or stable internal conditions.
When you get too hot or too cold, the brain alerts the rest of the body. It sends messages that either cool
you off or warm you up. On a very cold day you may start shivering. The heat control center in the brain has
sent a message to your muscles to move very rapidly. When muscles shiver more heat can be given off. The
extra heat helps to keep you warm.