Download The Neuron: Building Block of the Nervous System

The Neuron
 The building block of the
nervous system.
 Neuron – A cell
specialized to receive,
process, and transmit
information to other
cells.
 Bundles of neurons are
called nerves.
Types of Neurons
 Sensory (afferent) Neurons – Act like one-way streets
that carry traffic from the sense organs toward the
brain.
 Treat the brain to sight, taste, hearing, touch, smell,
pain, and balance.
 Ex. – When you test the water temperature in the
shower with your hand, afferent neurons carry the
message toward the brain.
Types of Neurons
 Motor (efferent)Neurons – Form the one-way routes
that transport messages away from the brain to the
muscles, organs, and glands
 Ex – In our shower example, motor neurons deliver the
message from the brain that tells your hand just how
much to move the shower control knob.
Types of Neurons
 Interneurons – Relays
messages between other
neurons, especially in
the brain and spinal
cord.
 Brain is basically a
network of billions of
intricately connected
interneurons.
How Neurons Work
 Dendrites – A branched
fiber that extends
outward from the main
cell body and carries
information into the
neuron.
 Act like a net that
collects messages.
How Neurons Work
 Soma – Part of the
neuron containing the
nucleus.
 Receiving information
from the dendrites and
then makes the decision
to either pass the
information on or stop
it.
How Neurons Work
 Axon – An extended fiber
that conducts
information from the
soma to the terminal
buttons. Information
travels along the axon in
the form of an electric
charge called the action
potential.
The Resting Potential
 Resting Potential – The electrical charge of the
axon in its inactive state, when the neuron is
ready to fire.
 http://www.youtube.com/watch?v=YP_P6bYvEj
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The Action Potential
 Action Potential – The nerve
impulse caused by a change in
the electrical charge across the
cell membrane of the axon.
 When the neuron fires, this
charge travels down the axon
and causes
neurotransmitters to be
released by the terminal
buttons.
 Sets off a chain reaction like a
set of falling dominos.
The Action Potential
 All-or-None Principle – Refers to the fact that the
action potential in the axon occurs either full-blown or
not at all.
Synaptic Transmission
 Synapse – The
microscopic gap that
serves as a
communications link
between neurons.
 Synapses also occur
between neurons and
the muscles or glands
they serve.
Synaptic Transmission
 Terminal Buttons – Tiny
bulblike structures at the
end of the axon
 Contain
neurotransmitters that
carry the neuron’s
message into the
synapse.
Synaptic Transmission
 Synaptic Transmission – Sequence of events in which
the electrical message morphs into a chemical
message that easily flows across the synaptic gap or
cleft between neurons.
Neurotransmitters
 Neurotransmitters –
Chemical messengers
that relay neural
messages across the
synapse. Many
neurotransmitters are
also hormones.
Plasticity
 Plasticity – The nervous system’s ability to
adapt or change as the result of experience.
 Plasticity may also help the nervous system
adapt to physical damage.
 Hugely important in helping us survive.
Glial Cells
 Glial Cells – Cells that
bind the neurons
together.
 Also provide an
insulating cover (the
myelin sheath) of the
axon for some neurons,
which facilitates the
electrical impulse.