Cognitive Psychology: Connecting Mind, Research and Everyday Experience, 3rd Edition

Neurons: The Building Blocks of the Nervous System • 25

Neurons: The Building Blocks of the Nervous System

How is it possible that the 3.5-pound structure called the brain could be the seat of the

mind? It is, after all, just static tissue. It has no moving parts (like the heart). It doesn’t

expand or contract (like the lungs), and when observed with the naked eye it looks

almost solid. As it turns out, to understand the relation between the brain and the mind

it is necessary to look within the brain and observe the small units that make up its

structure and the electrical signals that travel in these units.

THE MICROSTRUCTURE OF THE BRAIN: NEURONS

For many years, the nature of the brain’s tissue was a mystery. Looking at the interior

of the brain with the unaided eye gave no indication that it is made up of billions of

smaller units. The nature of electrical signals in the brain and the pathways over which

they traveled were just beginning to be discovered in the 19th century.

● FIGURE 2.1 Some of the

physiological processes that

occur as Juan turns off his alarm.

(a) Sound waves are changed to

electrical signals in the ear and

are sent to the brain.

(b) Signals reaching the auditory

areas of the brain—which are

located inside the brain, under

the hatched area—cause Juan

to hear the alarm. (c) After Juan

hears the alarm, signals are

sent to the motor area. The two

arrows pointing up symbolize

the fact that these signals reach

the motor area along a number

of diff erent pathways. Signals are

then sent from the motor area to

muscles in Juan’s arm and hand

so he can turn off the alarm.

(a) Sound to electricity

(b) Hearing

(c) Reaction

Signals reach

auditory area

Signals to arm and hand

Motor area

To motor

area

To motor

area

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