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What is the purpose of the
Nervous system?
To receive
information from
a sensory neuron
To process
info. by the
brain & spinal cord
To respond by an
effectors
(muscle/gland)
What are 2 divisions of the
nervous system?

Central Nervous system
 Brain
 Spinal cords

Peripheral Nervous System
 All other nerve cells
What is the basic unit of the
nervous system?

Neuron
• Dendrites
receive stimuli
• Axon transmits
the impulse to
another
dendrite
• Synapse
• How neurons
connect
Types of neurons
17-5
Neuron Structure
Neurons are composed of dendrites that
receive signals, a cell body with a nucleus,
and an axon that conducts a nerve impulse
away.
Sensory neurons take information from sensory
receptors to the CNS.
Interneurons occur within the CNS and
integrate input (nonmyelinated).
Motor neurons take information from the CNS
to muscles or glands.
17-6
How does the Synapse carry the signal?
1. Electrical current travels down the axon
2. Vesicles with chemicals move toward the membrane what is that called?
3. Chemicals are released and diffuse toward the next
cell’s plasma membrane
4. The chemicals open up the transport proteins and allow
the signal to pass to the next cell - what type of diffusion
is this?
What do you think can change
neurons and their connections?
Accidents
 Drugs
 Alcohol
 Disease

Drugs and alcohol bind important receptors on neurons
Repeated binding causes the neuron to die
100 Billion or so neurons - what’s the
problem with some of them dying?
•Cells multiply all the time
- will your neurons?
•Does everyone react the
same way to accidents, or
drugs and alcohol?
•Do all organisms react the
same to all stimulus?
•Which of your activities
use your neurons?
Drugs = neuron death
What if neurons die here?
or here
or here
or here
or here