Page 112 - The Cell in 40 Topics

he links between neurons, or nerve cells, are established both
by electrical signals and by means of chemical signals. Both
forms of communication contain significant marvels.
In this section we shall be concentrating on various aspects of chemi-
cal communication, established by messenger molecules that comprise the
spinal neurotransmitter. These are produced in the body of the nerve cell,
carried along the axons (the long arms of neurons), and stored in miniature
“bubbles” at the axons’ terminals. Each bubble contains some 5,000 mes-
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senger molecules. And recent research has shown that every neuron pro-
20
duces different chemical messengers. To put it another way, it resembles a
chemical plant in which the various tools to be used in communication are
produced (Figure 89).
The neuron that transmits the signal may be described as the transmit-
ter and the receiving neuron as the receiver. These two come face to face at
the synapse junctions. The distance between them is approximately 0.00003
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millimeters (1.1811 inches). The electrical signal sets in motion the mes-
sengers at the end of the nerve-cell axons. Bubbles filled with chemical mes-

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