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Module 1.3a

Other modules explore neurotransmitter influences on hunger and thinking, depres- ®
sion and euphoria, and addictions and therapy. For now, let’s see how neurotransmitters AP Exam Tip
influence our motions and emotions. A particular brain pathway may use only one or two
neurotransmitters, such as serotonin and dopamine, and particular neurotransmitters As the text indicates, there are
dozens of different neurotrans-
(depending on their brain locations) affect specific behaviors and emotions (Table 1.3-1). mitters. Though there’s no way to
But neurotransmitter systems don’t operate in isolation; they interact, and their effects vary predict exactly which ones you’ll
®
with the receptors they stimulate (Figure 1.3-5). need to know on the AP exam,
it’s quite likely you will be asked
about the neurotransmitters in
Table 1.3-1.
TABLE 1.3-1 Commonly Studied Neurotransmitters and Their Functions

Neurotransmitter Function Examples of Malfunctions

Acetylcholine (ACh) Enables muscle action, With Alzheimer’s disease, ACh-producing
learning, and memory neurons deteriorate.
Copyright © Bedford, Freeman & Worth Publishers.
Dopamine Influences movement, Oversupply linked to schizophrenia.
learning, attention, and Undersupply linked to tremors and
emotion decreased mobility in Parkinson’s disease.
Serotonin Affects mood, hunger, Undersupply linked to depression. Some
sleep, and arousal drugs that raise serotonin levels are used Noam Galai/Getty Images ASSOCIATED PRESS
to treat depression.

Norepinephrine Helps control alertness Undersupply can depress mood.
and arousal Dependent upon dopamine The
neurotransmitter dopamine helps
GABA (gamma- A major inhibitory Undersupply linked to seizures, tremors, us move, think, and feel. Too
little dopamine may produce the
aminobutyric acid) neurotransmitter and insomnia. tremors and loss of motor control of
Parkinson’s disease (National Institute
Oversupply can overstimulate the brain,
Glutamate Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
A major excitatory
on Aging [NIA], 2019; Weinstein et al.,
neurotransmitter; involved producing migraines or seizures. 2018). More than 10 million people
in memory worldwide have Parkinson’s disease,
including actor Michael J. Fox and
Endorphins Neurotransmitters that Oversupply with opioid drugs can the late boxing legend Muhammad Ali
influence the perception of suppress the body’s natural endorphin (Parkinson’s Foundation, 2018).
pain or pleasure supply.
Substance P Involved in pain perception Oversupply can lead to chronic pain.
and immune response

Figure 1.3-5
Neurotransmitter pathways
Each of the brain’s differing
chemical messengers has
designated pathways where
it operates, as shown here for
serotonin and dopamine (Carter,
1998).

Macmillan Learning Macmillan Learning

Dopamine pathway Serotonin pathway

The Neuron and Neural Firing: Neural Communication and the Endocrine System Module 1.3a 33

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