Page: Textbook - Chapter 4

4. Brains, Bodies, and Behaviour

Did a Neurological Disorder Cause a Musician to Compose Boléro and an Artist to Paint It 66 Years

Later?

In 1986, Anne Adams was working as a cell biologist at the University of Toronto in Ontario, Canada. She

took a leave of absence from her work to care for a sick child, and while she was away, she completely

changed her interests, dropping biology entirely and turning her attention to art. In 1994 she completed

her painting Unravelling Boléro, a translation of Maurice Ravel’s famous orchestral piece onto canvas.

As you can see on the New Scientist website (http://www.newscientist.com/data/images/ns/cms/dn13599/

dn13599-1_567.jpg), this artwork is filled with themes of repetition. Each bar of music is represented by

a lacy vertical figure, with the height representing volume, the shape representing note quality, and the

colour representing the music’s pitch. Like Ravel’s music (see the video below), which is a hypnotic piece

consisting of two melodial themes repeated eight times over 340 musical bars, the theme in the painting

repeats and builds, leading to a dramatic change in colour from blue to orange and pink, a representation of

Boléro’s sudden and dramatic climax.

Maurice Ravel’s composition Boléro (1928) [YouTube]:

http://www.youtube.com/watch?v=3-4J5j74VPw

This is a video clip of Maurice Ravel’s Boléro, composed in 1928 during the

early phase of his illness.

Shortly after finishing the painting, Adams began to experience behavioural

problems, including increased difficulty speaking. Neuroimages of Adams’s

brain taken during this time show that regions in the front part of her brain,

which are normally associated with language processing, had begun to

deteriorate, while at the same time, regions of the brain responsible for the

integration of information from the five senses were unusually well developed (Seeley et al., 2008). The

deterioration of the frontal cortex is a symptom of frontotemporal dementia, a disease that is associated with

changes in artistic and musical tastes and skills (Miller, Boone, Cummings, Read, & Mishkin, 2000), as well

as with an increase in repetitive behaviours (Aldhous, 2008).

What Adams did not know at the time was that her brain may have been undergoing the same changes

that Ravel’s had undergone 66 years earlier. In fact, it appears that Ravel may have suffered from the

same neurological disorder. Ravel composed Boléro at age 53, when he himself was beginning to show

behavioural symptoms that were interfering with his ability to move and speak. Scientists have concluded,

based on an analysis of his written notes and letters, that Ravel was also experiencing the effects of

frontotemporal dementia (Amaducci, Grassi, & Boller, 2002). If Adams and Ravel were both affected by the

same disease, this could explain why they both became fascinated with the repetitive aspects of their arts,

and it would present a remarkable example of the influence of our brains on behaviour.

117

Every behaviour begins with biology. Our behaviours, as well as our thoughts and feelings, are produced by the

actions of our brains, nerves, muscles, and glands. In this chapter we will begin our journey into the world of

psychology by considering the biological makeup of the human being, including the most remarkable of human

organs—the brain. We’ll consider the structure of the brain and also the methods that psychologists use to study the

brain and to understand how it works.

We will see that the body is controlled by an information highway known as the nervous system, a collection of

hundreds of billions of specialized and interconnected cells through which messages are sent between the brain and

the rest of the body. The nervous system consists of the central nervous system (CNS), made up of the brain and

the spinal cord, and the peripheral nervous system (PNS), the neurons that link the CNS to our skin, muscles, and

glands. And we will see that our behaviour is also influenced in large part by the endocrine system, the chemical

regulator of the body that consists of glands that secrete hormones.

Although this chapter begins at a very low level of explanation, and although the topic of study may seem at

first to be far from the everyday behaviours that we all engage in, a full understanding of the biology underlying

psychological processes is an important cornerstone of your new understanding of psychology. We will consider

throughout the chapter how our biology influences important human behaviours, including our mental and physical

health, our reactions to drugs, as well as our aggressive responses and our perceptions of other people. This

chapter is particularly important for contemporary psychology because the ability to measure biological aspects of

behaviour, including the structure and function of the human brain, is progressing rapidly, and understanding the

biological foundations of behaviour is an increasingly important line of psychological study.

References

Aldhous, P. (2008, April 7). “Boléro”: Beautiful symptom of a terrible disease. New Scientist. Retrieved

from http://www.newscientist.com/article/dn13599-bolero-beautiful-symptom-of-a-terrible-disease.html

Amaducci, L., Grassi, E., & Boller, F. (2002). Maurice Ravel and right-hemisphere musical creativity: Influence of

disease on his last musical works? European Journal of Neurology, 9(1), 75–82.

Miller, B. L., Boone, K., Cummings, J. L., Read, S. L., & Mishkin, F. (2000). Functional correlates of musical and

visual ability in frontotemporal dementia. British Journal of Psychiatry, 176, 458–463.

Seeley, W. W., Matthews, B. R., Crawford, R. K., Gorno-Tempini, M. L., Foti, D., Mackenzie, I. R., & Miller, B. L.

(2008). “Unravelling Boléro”: Progressive aphasia, transmodal creativity, and the right posterior neocortex. Brain,

131(1), 39–49.

4. BRAINS, BODIES, AND BEHAVIOUR • 118

4.1 The Neuron Is the Building Block of the Nervous System

Learning Objectives

1. Describe the structure and functions of the neuron.

2. Draw a diagram of the pathways of communication within and between neurons.

3. List three of the major neurotransmitters and describe their functions.

The nervous system is composed of more than 100 billion cells known as neurons. A neuron is a cell in the nervous

system whose function it is to receive and transmit information. As you can see in Figure 4.1, “Components of the

Neuron,” neurons are made up of three major parts: a cell body, or soma, which contains the nucleus of the cell and

keeps the cell alive; a branching treelike fibre known as the dendrite, which collects information from other cells

and sends the information to the soma; and a long, segmented fibre known as the axon, which transmits information

away from the cell body toward other neurons or to the muscles and glands. Figure 4.2 shows a photograph of

neurons taken using confocal microscopy.

Figure 4.1 Components of the Neuron.

Some neurons have hundreds or even thousands of dendrites, and these dendrites may themselves be branched to

allow the cell to receive information from thousands of other cells. The axons are also specialized, and some, such

as those that send messages from the spinal cord to the muscles in the hands or feet, may be very long — even up

to several feet in length. To improve the speed of their communication, and to keep their electrical charges from

119

Figure 4.2 The nervous system, including the brain, is made up of billions of interlinked neurons.

This vast interconnected web is responsible for all human thinking, feeling, and behaviour.

shorting out with other neurons, axons are often surrounded by a myelin sheath. The myelin sheath is a layer of

fatty tissue surrounding the axon of a neuron that both acts as an insulator and allows faster transmission of the

electrical signal. Axons branch out toward their ends, and at the tip of each branch is a terminal button.

Neurons Communicate Using Electricity and Chemicals

The nervous system operates using an electrochemical process. An electrical charge moves through the neuron

itself, and chemicals are used to transmit information between neurons. Within the neuron, when a signal is received

by the dendrites, it is transmitted to the soma in the form of an electrical signal, and, if the signal is strong enough,

it may then be passed on to the axon and then to the terminal buttons. If the signal reaches the terminal buttons,

they are signalled to emit chemicals known as neurotransmitters, which communicate with other neurons across the

spaces between the cells, known as synapses.

The following video clip shows a model of the electrochemical action of the neuron

and neurotransmitters:

The Electrochemical Action of the Neuron [YouTube]: http://www.youtube.com/

watch?v=TKG0MtH5crc

The electrical signal moves through the neuron as a result of changes in the electrical

charge of the axon. Normally, the axon remains in the resting potential, a state in

which the interior of the neuron contains a greater number of negatively charged ions

than does the area outside the cell. When the segment of the axon that is closest to the

cell body is stimulated by an electrical signal from the dendrites, and if this electrical signal is strong enough that it

4.1 THE NEURON IS THE BUILDING BLOCK OF THE NERVOUS SYSTEM • 120

passes a certain level or threshold, the cell membrane in this first segment opens its gates, allowing positively

charged sodium ions that were previously kept out to enter. This change in electrical charge that occurs in a

neuron when a nerve impulse is transmitted is known as the action potential. Once the action potential occurs, the

number of positive ions exceeds the number of negative ions in this segment, and the segment temporarily becomes

positively charged.

As you can see in Figure 4.3, “The Myelin Sheath and the Nodes of Ranvier,” the axon is segmented by a series

of breaks between the sausage-like segments of the myelin sheath. Each of these gaps is a node of Ranvier.

1 The

electrical charge moves down the axon from segment to segment, in a set of small jumps, moving from node to

node. When the action potential occurs in the first segment of the axon, it quickly creates a similar change in the next

segment, which then stimulates the next segment, and so forth as the positive electrical impulse continues all the

way down to the end of the axon. As each new segment becomes positive, the membrane in the prior segment closes

up again, and the segment returns to its negative resting potential. In this way the action potential is transmitted

along the axon, toward the terminal buttons. The entire response along the length of the axon is very fast — it can

happen up to 1,000 times each second.

Figure 4.3 The Myelin Sheath and the Nodes of Ranvier. The myelin sheath wraps around the

axon but also leaves small gaps called the nodes of Ranvier. The action potential jumps from node

to node as it travels down the axon.

An important aspect of the action potential is that it operates in an all or nothing manner. What this means is that

the neuron either fires completely, such that the action potential moves all the way down the axon, or it does not fire

at all. Thus neurons can provide more energy to the neurons down the line by firing faster but not by firing more

strongly. Furthermore, the neuron is prevented from repeated firing by the presence of a refractory period — a

brief time after the firing of the axon in which the axon cannot fire again because the neuron has not yet returned

to its resting potential.

Neurotransmitters: The Body’s Chemical Messengers

Not only do the neural signals travel via electrical charges within the neuron, but they also travel via chemical

transmission between the neurons. Neurons are separated by junction areas known as synapses,

2 areas where the

terminal buttons at the end of the axon of one neuron nearly, but don’t quite, touch the dendrites of another.

The synapses provide a remarkable function because they allow each axon to communicate with many dendrites

in neighbouring cells. Because a neuron may have synaptic connections with thousands of other neurons, the

communication links among the neurons in the nervous system allow for a highly sophisticated communication

system.

When the electrical impulse from the action potential reaches the end of the axon, it signals the terminal buttons

to release neurotransmitters into the synapse. A neurotransmitter is a chemical that relays signals across the

synapses between neurons. Neurotransmitters travel across the synaptic space between the terminal button of

one neuron and the dendrites of other neurons, where they bind to the dendrites in the neighbouring neurons.

121 • INTRODUCTION TO PSYCHOLOGY - 1ST CANADIAN EDITION

Furthermore, different terminal buttons release different neurotransmitters, and different dendrites are particularly

sensitive to different neurotransmitters. The dendrites will admit the neurotransmitters only if they are the right

shape to fit in the receptor sites on the receiving neuron. For this reason, the receptor sites and neurotransmitters are

often compared to a lock and key (Figure 4.4, “The Synapse”).

Figure 4.4 The Synapse. When the nerve impulse reaches the terminal button, it triggers the

release of neurotransmitters into the synapse. The neurotransmitters fit into receptors on the

receiving dendrites in the manner of a lock and key.

When neurotransmitters are accepted by the receptors on the receiving neurons, their effect may be either excitatory

(i.e., they make the cell more likely to fire) or inhibitory (i.e., they make the cell less likely to fire). Furthermore,

if the receiving neuron is able to accept more than one neurotransmitter, it will be influenced by the excitatory

and inhibitory processes of each. If the excitatory effects of the neurotransmitters are greater than the inhibitory

influences of the neurotransmitters, the neuron moves closer to its firing threshold; if it reaches the threshold, the

action potential and the process of transferring information through the neuron begins.

Neurotransmitters that are not accepted by the receptor sites must be removed from the synapse in order for the

next potential stimulation of the neuron to happen. This process occurs in part through the breaking down of the

neurotransmitters by enzymes, and in part through reuptake, a process in which neurotransmitters that are in the

synapse are reabsorbed into the transmitting terminal buttons, ready to again be released after the neuron fires.

More than 100 chemical substances produced in the body have been identified as neurotransmitters, and these

substances have a wide and profound effect on emotion, cognition, and behaviour. Neurotransmitters regulate our

4.1 THE NEURON IS THE BUILDING BLOCK OF THE NERVOUS SYSTEM • 122

appetite, our memory, our emotions, as well as our muscle action and movement. And as you can see in Table 4.1,

“The Major Neurotransmitters and Their Functions,” some neurotransmitters are also associated with psychological

and physical diseases.

Drugs that we might ingest — either for medical reasons or recreationally — can act like neurotransmitters to

influence our thoughts, feelings, and behaviour. An agonist is a drug that has chemical properties similar to a

particular neurotransmitter and thus mimics the effects of the neurotransmitter. When an agonist is ingested, it

binds to the receptor sites in the dendrites to excite the neuron, acting as if more of the neurotransmitter had been

present. As an example, cocaine is an agonist for the neurotransmitter dopamine. Because dopamine produces

feelings of pleasure when it is released by neurons, cocaine creates similar feelings when it is ingested. An

antagonist is a drug that reduces or stops the normal effects of a neurotransmitter. When an antagonist is ingested,

it binds to the receptor sites in the dendrite, thereby blocking the neurotransmitter. As an example, the poison

curare is an antagonist for the neurotransmitter acetylcholine. When the poison enters the brain, it binds to the

dendrites, stops communication among the neurons, and usually causes death. Still other drugs work by blocking

the reuptake of the neurotransmitter itself — when reuptake is reduced by the drug, more neurotransmitter remains

in the synapse, increasing its action.

Table 4.1 The Major Neurotransmitters and Their Functions

[Skip Table]

Neurotransmitter Description and function Notes

Acetylcholine

(ACh)

A common neurotransmitter used in

the spinal cord and motor neurons to

stimulate muscle contractions. It’s

also used in the brain to regulate

memory, sleeping, and dreaming.

Alzheimer’s disease is associated with an undersupply of

acetylcholine. Nicotine is an agonist that acts like acetylcholine.

Dopamine

Involved in movement, motivation,

and emotion, Dopamine produces

feelings of pleasure when released by

the brain’s reward system, and it’s

also involved in learning.

Schizophrenia is linked to increases in dopamine, whereas

Parkinson’s disease is linked to reductions in dopamine (and

dopamine agonists may be used to treat it).

Endorphins

Released in response to behaviours

such as vigorous exercise, orgasm,

and eating spicy foods.

Endorphins are natural pain relievers. They are related to the

compounds found in drugs such as opium, morphine, and

heroin. The release of endorphins creates the runner’s high that

is experienced after intense physical exertion.

GABA (gammaaminobutyric

acid)

The major inhibitory

neurotransmitter in the brain.

A lack of GABA can lead to involuntary motor actions,

including tremors and seizures. Alcohol stimulates the release of

GABA, which inhibits the nervous system and makes us feel

drunk. Low levels of GABA can produce anxiety, and GABA

agonists (tranquilizers) are used to reduce anxiety.

Glutamate

The most common neurotransmitter,

it’s released in more than 90% of the

brain’s synapses. Glutamate is found

in the food additive MSG

(monosodium glutamate).

Excess glutamate can cause overstimulation, migraines, and

seizures.

Serotonin

Involved in many functions,

including mood, appetite, sleep, and

aggression.

Low levels of serotonin are associated with depression, and

some drugs designed to treat depression (known as selective

serotonin reuptake inhibitors, or SSRIs) serve to prevent their

reuptake.

123 • INTRODUCTION TO PSYCHOLOGY - 1ST CANADIAN EDITION

Key Takeaways

• The central nervous system (CNS) is the collection of neurons that make up the brain and the

spinal cord.

• The peripheral nervous system (PNS) is the collection of neurons that link the CNS to our skin,

muscles, and glands.

• Neurons are specialized cells, found in the nervous system, which transmit information. Neurons

contain a dendrite, a soma, and an axon.

• Some axons are covered with a fatty substance known as the myelin sheath, which surrounds the

axon, acting as an insulator and allowing faster transmission of the electrical signal.

• The dendrite is a treelike extension that receives information from other neurons and transmits

electrical stimulation to the soma.

• The axon is an elongated fibre that transfers information from the soma to the terminal buttons.

• Neurotransmitters relay information chemically from the terminal buttons and across the synapses

to the receiving dendrites using a lock and key type of system.

• The many different neurotransmitters work together to influence cognition, memory, and

behaviour.

• Agonists are drugs that mimic the actions of neurotransmitters, whereas antagonists are drugs that

block the actions of neurotransmitters.

Exercises and Critical Thinking

1. Draw a picture of a neuron and label its main parts.

2. Imagine an action that you engage in every day and explain how neurons and neurotransmitters

might work together to help you engage in that action.

Image Attributions

Figure 4.2: “Confocal microscopy of mouse brain, cortex” by ZEISS Microscopy (http://www.flickr.com/photos/

zeissmicro/10799674936/in/photostream/) used under CC BY-NC-ND 2.0 (http://creativecommons.org/licenses/

by-nc-nd/2.0/deed.en_CA) license.

Notes

1. The break in the myelin sheath of a nerve fibre.

4.1 THE NEURON IS THE BUILDING BLOCK OF THE NERVOUS SYSTEM • 124

2. The small gap between neurons across which nerve impulses are transmitted.

125 • INTRODUCTION TO PSYCHOLOGY - 1ST CANADIAN EDITION