Transcript Nervous System Notes

Nervous System Notes
Ch. 19.1
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!
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.
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.
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
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.
The Neuron
• Neuron is the name for Nerve Cells!
• They carry messages around your body!
• These messages are called Nerve
Impulses!
Neuron Structure
• The neuron is made of 3 major sections:
– The cell body
– Axon
– Axon tips
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”.
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
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.
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.
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!)
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!
The Synapse
• After the nerve impulse reaches
the axon tip, there is a space
between neurons!
• This space is the synapse!
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!