Download NT Notes

This powerpoint will help you with your
WS and with the computer based activity.
You do not need to memorize this info,
just understand it as we discuss it. Later:
you will have a reference sheet to look at
while you do your WS. This is a class set
so please do not take them with you. It is
also available on the webpage along with
this powerpoint.
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Neurotransmitter: A chemical or peptide
substance that transmits nerve impulses across
synapses (space between two
neurons), that effect motor coordination, mood,
behavior, and other physiological activities,
such as heart rate.
Different types of NT have different actions
based on tissue type, receptor type, etc.
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Scientists have identified at least fifty
neurotransmitters in the nervous system, and
there may be several dozen more.
There are four groups of neurotransmitters:
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1) acetylcholine,
2) amino acids,
3) biogenic monoamines, and
4) neuropeptides.
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Neurotransmitters are classified as excitatory or
inhibitory according to their effects on
postsynaptic membranes.
Excitatory: if activation of the receptor causes
depolarization of the membrane and promotes action
potential generation.
 Inhibitory: if the activation of the receptor causes
hyperpolarization and depresses action potential
generation
Important Point:
 So: release of an NT may cause something to happen OR
cause it not to happen!!
 AND an action potential may cause something to happen
OR cause it not to happen!!
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After the release of the NT: It is necessary to
turn OFF the signal to control the activity at the
synapse
Enzymatic Breakdown: An enzyme can break
down the neurotransmitter chemical into its
component parts,
Reuptake: the presynaptic neuron can have
transporters, which suck the neurotransmitter
up back into the synaptic buton, either to be
shoved back into vesicles, or to be degraded
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A. Disrupt the synthesis of neurotransmitter. A
drug can block a cell's ability to manufacture the
neurotransmitter, thus decreasing its availability.
B. Disrupt the transport of neurotransmitter to
axon terminal. Once a neuron has manufactured a
neurotransmitter, the transmitter needs to be
stored in vesicles near the terminal end of the
neuron for it to be released. A drug can block this
transportation from occurring, thus decreasing the
neurotransmitter's availability.
.
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C. Affect storage of the neurotransmitter. A drug
can make the storage vesicles "leaky", allowing
neurotransmitter to be destroyed within the
cell. This will reduce the availability of the
neurotransmitter in the synapse.
D. Cause premature release of
neurotransmitter. By forcing neurotransmitter
into the synapse without the nerve firing, the
immediate effect will be an increase in
neurotransmitter availability in the synapse. If this
happens for too long, the forced release will
outstrip the neuron's ability to manufacture the
neurotransmitter, leading to decreased availability
in the long run.
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E. Blocks reuptake of neurotransmitter. By
stopping the releasing cell from taking the
released neurotransmitter back into the cell, the
neurotransmitter remains available within the
synapse.
F. Disrupt the actions of enzymes. By
stopping the enzymes from breaking down
released neurotransmitters, the
neurotransmitter remains available within the
synapse.
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Let's check this idea using one neurotransmitter as
an example: norepinephrine. As you may recall,
norepinephrine is an excitatory neurotransmitter
that has effects in the sympathetic nervous system
and in the brain. In the brain, norepinephrine has
mood and other effects.
Increased levels of norepinephrine result in increased
sympathetic nervous system activity, such as increased
heart rate and blood pressure, and is related to
heightened emotional arousal, including excitement and
anxiety.
Decreased levels of norepinephrine result in decreases
in sympathetic nervous system activity and are related
to feelings of lethargy and depression.
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Quiz Time!!