Understanding Psychology (10th Ed)

mirror neurons
Specialized neurons 
that fi re not only when a person enacts 
a particular behavior, but also when a 
person simply observes another
individual carrying out the same 
behavior.
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 Module 
7 
Neurons: The Basic Elements of Behavior 
65
Where Neurons Meet: 
Bridging the Gap
If you have looked inside a computer, you’ve seen that each part is physically con-
nected to another part. In contrast, evolution has produced a neural transmission 
system that at some points has no need for a structural connection between its com-
ponents. Instead, a chemical connection bridges the gap, known as a synapse, between 
two neurons (see Figure 4). The
 synapse 
is the space between two neurons where 
the axon of a sending neuron communicates with the dendrites of a receiving neuron 
by using chemical messages (Dean & Dresbach, 2006; Fanselow & Poulos, 2005). 
When a nerve impulse comes to the end of the axon and reaches a terminal 
button, the terminal button releases a chemical courier called a neurotransmitter. 
 Neurotransmitters 
are chemicals that carry messages across the synapse to a dendrite 
synapse
The space between two 
neurons where the axon of a sending 
neuron communicates with the 
dendrites of a receiving neuron by 
using chemical messages.
FIGURE 4
A synapse is the junction between an axon and a dendrite. The gap between 
the axon and the dendrite is bridged by chemicals called neurotransmitters (Mader, 2000). In 
(a) read Step 1 through Step 4 to follow this process. (b) Just as the pieces of a jigsaw puzzle 
can fi t in only one specifi c location in a puzzle, each kind of neurotransmitter has a distinctive 
confi guration that allows it to fi t into a specifi c type of receptor cell (Johnson, 2000). Why is it 
advantageous for axons and dendrites to be linked by temporary chemical bridges rather 
than by the hard wiring typical of a radio connection or telephone hookup?
Axon
Synapse
Dendrite