Understanding Psychology (10th Ed)

FIGURE 5
Major neurotransmitters.
Serotonin pathways
Dopamine pathways
Neurotransmitter
Function
Muscle movement,
cognitive functioning
Memory
Eating, aggression, sleeping
Movement control,
pleasure and reward,
attention
Sleeping, eating, mood,
pain, depression
Pain suppression,
pleasurable feelings,
appetites, placebos
Effect
Excitatory in brain and
autonomic nervous
system; inhibitory
elsewhere
Excitatory
Main inhibitory
neurotransmitter
Inhibitory or excitatory
Inhibitory
Primarily inhibitory,
except in hippocampus
Location
Brain, spinal cord, peripheral
nervous system, especially
some organs of the
parasympathetic nervous
system
Brain, spinal cord
Brain, spinal cord
Brain
Brain, spinal cord
Brain, spinal cord
Name
Acetylcholine (ACh)
Glutamate
Gamma-amino
butyric acid (GABA)
Dopamine (DA)
Serotonin
Endorphins
Michael J. Fox suff ers from Parkinson’s 
disease, and has become a strong 
advocate for research into the disorder.
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68 Chapter 
3 
Neuroscience and Behavior
In other instances, over production of dopamine produces negative consequences. 
For example, researchers have hypothesized that schizophrenia and some other 
severe mental disturbances are affected or perhaps even caused by the presence of 
unusually high levels of dopamine. Drugs that block the reception of dopamine 
reduce the symptoms displayed by some people diagnosed with schizophrenia (Di 
Forti, Lappin, & Murray, 2007; Howes & Kapur, 2009; Murray, Lappin, & Di Forti, 
2008). 
Another neurotransmitter, serotonin , is associated with the regulation of sleep, 
eating, mood, and pain. A growing body of research points toward a broader role 
for serotonin, suggesting its involvement in such diverse behaviors as alcoholism, 
depression, suicide, impulsivity, aggression, and coping with stress (Carillo et al., 
2009; Murphy, Lappin, & Di Forti, 2008; Popa et al., 2008). 
Endorphins , another class of neurotransmitters, are a family of chemicals pro-
duced by the brain that are similar in structure to painkilling drugs such as mor-
phine. The production of endorphins refl ects the brain’s effort to deal with pain as 
well as to elevate mood. 
Endorphins also may produce the euphoric feelings that runners sometimes 
experience after long runs. The exertion and perhaps the pain involved in a long run 
may stimulate the production of endorphins, ultimately resulting in what has been 
called “runner’s high” (Kolata, 2002; Pert, 2002; Stanojevic, Mitic, & Vujic, 2007). 
Endorphin release might also explain other phenomena that have long puzzled 
psychologists. For example, the act of taking placebos (pills or other substances that 
contain no actual drugs but that patients believe will make them better) may induce 
the release of endorphins, leading to the reduction of pain (Crum & Langer, 2007; 
Rajagopal, 2006; Wager, 2005).
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