nervous system notes ch. 19.1. functions of the nervous system the nervous system receives...
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Nervous System Nervous System NotesNotes
Ch. 19.1
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Functions of the Nervous System
• The nervous system receives information about what is happening both inside and outside you body.
• It also tells your body to respond to information.
• It also helps maintain HOMEOSTASIS!
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Receiving Information
• Your nervous system tells you that something is happening around you:– Like a fly buzzing around your head.– Or the wind is blowing– Or a friend is telling a funny joke.
– It also checks your body for glucose levels or when you feel sick.
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Responding to Information
• Any change or signal in the environment that makes you react is called a stimulus.
• The fly buzzing is a stimulus.
• When your body REACTS, it is called a response!
• Swatting the fly is a response.
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Responding to Information
• There are 2 kinds of responses:
• Voluntary = things you think about doing:– Swatting the fly
• Involuntary = things your body does without thinking:– Heart beats, breathing in your sleep
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Maintaining Homeostasis
• The nervous system helps maintain Homeostasis by directing the body to respond appropriately to the information is receives.– If you are hungry, your nervous system tells
you to eat! = homeostasis!– Homeostasis = the things your body does to
keep you alive in that “just right” kind of way.
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The Neuron
• Neuron is the name for Nerve Cells!
• They carry messages around your body!
• These messages are called Nerve Impulses!
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Neuron Structure
• The neuron is made of 3 major sections:– The cell body– Axon– Axon tips
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Structure Cont.
• The Cell body contains– The nucleus (brain of the cell)– Dendrites (thread like extensions that catch
nerve impulses)• There can be MANY dendrites forming a large
“net”.
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Axon• The Axon carries the impulses toward
the next Neuron’s cell body.
• It’s like the highway the impulse takes from point A to point B.
• THERE IS ONLY 1 AXON PER NEURON
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Axon Tips
• The Axon tips shoot out charged chemicals that act like electricity in the body.
• These chemicals are the messages that are sent through your body.
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Kinds of Neurons
• 3 major kinds of neurons–Sensory Neurons
• These neurons “sense” your surroundings and send the message to your SPINAL CORD or BRAIN! They sense pressure or heat and cold.
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Cont.
–Interneurons• These neurons carry messages from
one neuron to the next neuron. “Middle Men”
–Motor Neurons• These connect to muscles or glands
to cause a response. (move leg muscle, sweat!)
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How a Nerve Impulse Travels
• Nerve impulses can travels as fast as 120 meters per second! THAT’S FAST!
• Messages travel from the Cell Body, down the axon, and to the axon tips!
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The Synapse
• After the nerve impulse reaches the axon tip, there is a space between neurons!
• This space is the synapse!
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How an Impulse is Transferred
• For a nerve impulse to be carried along at a synapse, it must cross the gap between the axon and the next structure.
• The axon tips release chemicals that carry the impulse across the gap.
• It’s like a car trying to get from one side of the river to the next on a ferry boat!