Download Neurons and Neuronal Communication

9/11/2013
Neural and Hormonal Systems
Module 3
Why?
Definition of Psychology?
Approach?
By studying the links between biological
activity and psychological events, biological
psychologists are gaining a better
understanding of how biology underlies our
behavior and mental processes.
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Neurons and Neuronal Communication:
The Structure of a Neuron
There are billions of neurons
(nerve cells) throughout the body.
When does the cell send the action
potential? When it reaches a threshold.
How neurons communicate
(with each other):
The
neuron
receives
signals
from other
neurons;
some are
telling it to
fire and
some are
telling it
not to fire.
• When the
threshold is
reached, the
action potential
starts moving.
• Like a gun, it
either fires or it
doesn’t
• This is known as
the “all-ornone” response.
The
action
potential
travels
down the
axon
from the
cell body
to the
terminal
branches
.
Neurottransmi
-tters
(chemical
messengers)
are released
and cross a
tiny gap to
reach the
receiving
neuron.
The threshold is reached when
excitatory (“Fire!”) signals
outweigh the inhibitory (“Don’t
fire!”) signals by a certain amount.
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The Synapse
The synapse is a
junction between the
axon tip of the
sending neuron and
the dendrite or cell
body of the receiving
neuron.
The synapse is
also known as the
“synaptic
junction” or
“synaptic gap.”
Neurotransmitters
Neurotransmitter
s are chemicals
used to send a
signal across the
synaptic gap.
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Reuptake:
Recycling Neurotransmitters [NTs]
Reuptake:
After the neurotransmitters
stimulate the receptors on
the receiving neuron, the
chemicals are taken back
up into the sending neuron
to be used again.
Neurons
Dendrites: the neuron’s bushy, branching extensions
that receive messages and conduct impulses toward the
cell body.
Axon: the neuron’s extension that passes messages
through its branching terminal fibers that form
junctions with other neurons, muscles, or glands.
Action Potential: a neural impulse; a brief electrical
charge that travels down an axon.
Excitatory signals pushing a neuron’s accelerator
Inhibitory signals pushing a neuron’s brake
Excitatory signals – inhibitory signals > threshold an
action potential
Threshold: the level of stimulation required to trigger a
neural impulse
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How Neurons Communicate
Synapse [SIN-aps] the junction between the axon tip
of the sending neuron and the dendrite or cell body
of the receiving neuron. The tiny gap at this junction
is called the synaptic gap or cleft.
Neurotransmitters (chemicals) released from the
sending neuron travel across the synaptic gap and
bind to receptor sites on the receiving neuron,
thereby influencing it to generate an action potential.
Then, in a process called reuptake, the sending neuron
reabsorbs the excess neurotransmitters.
Neural Communication:
Seeing all the Steps Together
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