Understanding Psychology (10th Ed)

excitatory message
A chemical 
message that makes it more likely 
that a receiving neuron will fi re and 
an action potential will travel down 
its axon.
inhibitory message
A chemical 
message that prevents or decreases 
the likelihood that a receiving neuron 
will fi re.
reuptake
The reabsorption of neuro-
transmitters by a terminal button.
 Study Alert 
Remember this key fact: 
Messages inside neurons 
are transmitted in electrical 
form, whereas messages 
traveling between neurons 
travel via chemical means.
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 Module 
7 
Neurons: The Basic Elements of Behavior 
67
The same neurotransmitter, then, can act as an excitatory message to a neuron located 
in one part of the brain and can inhibit fi ring in neurons located in another part. 
(The major neurotransmitters and their effects are described in Figure 5.) 
One of the most common neurotransmitters is acetylcholine (or ACh , its chemical 
symbol), which is found throughout the nervous system. ACh is involved in our 
every move, because—among other things—it transmits messages relating to our 
skeletal muscles. ACh is also involved in memory capabilities, and diminished pro-
duction of ACh may be related to Alzheimer’s disease (Bazalakova et al., 2007; Mohapel 
et al., 2005). 
Another common excitatory neurotransmitter, glutamate , plays a role in memory. 
Memories appear to be produced by specifi c biochemical changes at particular syn-
apses, and glutamate, along with other neurotransmitters, plays an important role in 
this process (Carvalho, 2006; Riedel, Platt, & Micheau, 2003; Winters & Bussey, 2005). 
Gamma-amino butyric acid (GABA) , which is found in both the brain and the spi-
nal cord, appears to be the nervous system’s primary inhibitory neurotransmitter. It 
moderates a variety of behaviors, ranging from eating to aggression. Several common 
substances, such as the tranquilizer Valium and alcohol, are effective because they 
permit GABA to operate more effi ciently (Akirav, Raizel, & Maroun, 2006; Ball, 2004; 
Criswell et al., 2008; Lobo & Harris, 2008).
Another major neurotransmitter is dopamine (DA) , which is involved in move-
ment, attention, and learning. The discovery that certain drugs can have a signifi cant 
effect on dopamine release has led to the development of effective treatments for a 
wide variety of physical and mental ailments. For instance, Parkinson’s disease, from 
which actor Michael J. Fox suffers, is caused by a defi ciency of dopamine in the brain. 
Techniques for increasing the production of dopamine in Parkinson’s patients are 
proving effective (Antonini & Barone, 2008; Iversen & Iversen, 2007; Willis, 2005).