Download Physiological Mechanisms of Behavior

Lesson 2
Physiological Mechanisms of Behavior
Introduction: Connecting Your Learning
This lesson examines the structure and function of the nervous system and its connection to mind and
behavior. Aside from the study of genetic biology, the study of the brain is one of the fastest growing areas in
science today. The understanding of human nature is increasing by leaps and bounds as the workings of the
gene and the human brain are steadily unraveled.
The human brain is the most complicated physical object known to science. The interconnections in the brain
number at least into the trillions. The billions of neurons in the brain communicate with each other directly or
indirectly. Imagine a society of a hundred billion voices all talking to each other at once. How this great and
complex chorus of voices is orchestrated in a relatively coherent whole is one of the greatest questions in
science.
The brain and the nervous system are composed of a large set of localized subsystems, with each subsystem
involved in one or more basic biological or psychological activities, from vision and consciousness to hunger and
breathing. Understanding the brain and the nervous system is like learning a complex map of continents,
countries, counties, and cities – bigger areas contain smaller subsystems that, in turn, include even smaller
subsystems. As you learn the geography of the land (the anatomy), you also need to learn the functions or
activities (physiology) of each area. For every psychological process within a human being, a set of neural
systems is involved in that process. Without a brain, there is no mind.
Lectures and Readings
Media
Lecture
Yale Open Source Video: This Is Your Brain Lecture
Textbook
Readings
Chapter 5 – "The Neural Control of Behavior"
Focusing Your Learning
Course Competencies covered in this lesson:

Describe the relationship between the body, brain, and behavior.
Lesson Objectives
By the end of this lesson, you should be able to:
1. Describe the basic structures, functions, and biochemistry of the nervous system.
2. Discuss the effects of drugs.
3. Describe the basic structures and activities of the two hemispheres of the brain.
4. Discuss how experiences and changes in the brain affect behavior.
5. Discuss the similarities between the brains of humans and the brains of animals.
Approaching the Objectives
Chapter 5 introduces you to a biological perspective on psychology. This perspective will provide you with
many amazing practical benefits in the future. Physiological psychology clearly illustrates the scientific
dimension of the discipline of psychology. A great deal of factual information is provided in this section of the
course, and a variety of scientific technologies are introduced and described. Additionally, a number of
biological, chemical, and physical principles are discussed throughout the course. All of this scientific
information is connected to the mind and behavior, demonstrating clearly how humans can be scientifically
studied as part of the world of nature.
As you will see, the physiological perspective is relevant to all areas of psychology. Whether you are discussing
personality, development, or thinking, important facts concerning the brain and the functioning of the body
must be considered to understand a specific psychological topic.
Mind/Body Dilemma:
Hippocrates, the fourth-century B.C. Greek physician, challenged the popular notion of his time that the heart
was the center of human thoughts, emotions, sensations, and all that is considered psychological, according to
Gray; seventeenth-century philosopher and physiologist René Descartes challenged the popular notion of his
time that the soul was responsible for human movements, according to Bloom.
Both challenges led to unique results in modern psychology. Hippocrates' brain theory was correct: There is a
direct correlation between the brain and people's thoughts and behavior. Descartes' theory of dualism, (bodiesmaterial and minds-immaterial are separate entities) was successful for science because it unhinged the
concept that the soul was responsible for all human bodily movement. However, a consensus exists in the
scientific community that dualism is incorrect; neither "you" nor "I" exist separate from the body.
Refer back to Concluding Thoughts in Chapter 1: "The concept of the mind as a product of the brain." The
concept of "mind" continues to be debated in philosophy and psychology.
Consider this!
What are your thoughts on the mind/body dilemma? Do you agree with Descartes' theory or the
scientific community?
Human Nervous System
The human nervous system consists of the central nervous system (brain and spinal cord). The peripheral
nervous system (nerves) extends from the central nervous system. See Figure 5.1 on page 139 in your
textbook.
Bloom begins his discussion with the smallest part of the brain, the neurons.
Three Types of Neurons:
The body consists of three types of neurons: sensory neurons, motor neurons, and interneurons. Neurons are
the basic building blocks of mental states and behavior. The human brain contains approximately 100 billion
neurons, and each neuron is connected to roughly 100 trillion points of communication throughout the body.
Sensory neurons are bundled into nerves and carry information from sensory organs such as the eyes, nose,
ears, tongue, and skin to the central nervous system. Chapter 7 provides more discussion on the sensory
process.
Motor neurons are bundled into nerves and carry messages out from the central nervous system to operate
muscles and glands.
Interneurons exist entirely within the central nervous system and carry messages from one set of neurons to
another. They collect, organize, and integrate messages from various sources. Basically, interneurons do the
thinking, linking the sensation and action together.
Consider this!
So much of your mental activity, behavior, and experiences seem automatic to you. What
challenges would you face if your body could not experience pain?
Neurons on Drugs:
Bloom discusses the physiological and psychological effects of drugs. Drugs affect the neurons of your brain.
Bloom identifies five drugs and their specific effects on motor skills, cognition, and moods. You can read more in
your textbook. Additional discussion will follow when treatment options for mental disorders are discussed.
Neurons communicate by releasing a chemical substance, called a neurotransmitter, which alters the receiving
neuron. The receiving neurotransmitter is either excited or inhibited.
Drug
Physiological
Response
Psychological
Response
Curare
Inhibitory. Blocks motor
neutrons and skeletal
muscle cells. Motor
neutrons control
breathing. Death will
occur.
Amphetamines
Excitatory. Increase the
release of
norepinephrine and
dopamine.
Psychological high
Prozac
Excitatory. Increases
serotonin,
norepinephrine, and
dopamine by inhibiting
the enzyme that breaks
them down.
Alters mood, thoughts,
and perception
L-Dopa
Excitatory. Converted to
dopamine in the brain.
Minimizes loss and
destruction of motor
control. Treats
Parkinson's disease.
Alcohol
Inhibitory. Relaxes
frontal lobes and other
parts of your brain that
normally restrain
impulsive behavior.
Impairs judgment.
Increases aggression and
sexual desires.
Consider this!
Review "Hormones" (pp. 177-178). How are hormones similar to and different from
neurotransmitters?
The Brain:
Research has determined that the brain is not needed for all bodily activity. Descartes concluded that some
reflexes are mechanical. Bloom discusses research conducted by French psychologists on the bodies of
decapitated people. In these cases, the brain was not needed for all physiological responses, such as limb
flexion in withdrawal from pain or penis erection.
Three methods for identifying the functions of specific brain areas are:
1. Observing behavioral deficits that occur when a part of the brain is destroyed or is temporarily
inactivated.
2. Observing behavioral effects of artificially stimulating specific parts of the brain.
3. Recording changes in neural activity that occur in specific parts of the brain when a person or
animal is engaged in a particular mental or behavioral task.
Consider this!
Explain how abnormalities of the brain benefit the scientific study of brain functions.
Below are three parts of the brain and their functions discussed by Bloom. Continue reading Chapter 5 for
further explanation of the brain's components and the functions of each.
Medulla – heart rate and respiration
Cerebellum – body balance and muscular coordination
Hypothalamus – feeding, hunger, thirst, and sleep
Consider this!
Listen to Dr. Ralph DiLeone's discussion of "Food on the Brain*," which includes processes in the
brain that regulate eating.
Weight loss and dieting are a large industry in the U.S. Dr. DiLeone explains that the brain is
wired for pleasurable eating. What are your thoughts?
Hypothetically, if one part of the hypothalamus were manipulated for weight loss, what other
drives would be affected?
*This resource is accessible through the latest update of Quicktime or as a free download
through iTunes.
Two Hemispheres of the Brain:
The brain is divided into two hemispheres: left brain and right brain.
The Cerebral Cortex:
The cerebral cortex is the outer layer of the brain. It is divided into three categories: primary sensory areas,
primary motor areas, and association areas; and four lobes: frontal lobe, temporal lobe, occipital lobe, and
parietal lobe.
Consider this!
What are the functions of each category and lobe?
Topography of the Primary Sensory and Motor Sensory:
The organizational structure of the primary sensory and motor areas is known as the principle of topographic
organization. The two areas are situated close together which means they affect two areas that are close
together on the body. The adjacent neurons send and receive messages to the correlating areas. Bloom gives
an example of the tongue being closer to the jaw than to the hip. Review Figure 5.20 on page 161 which
illustrates this concept.
Consider this!
Review Figure 5.19 in your textbook. Compare the brains of four mammals. Describe their
differences and similarities.
Bloom's lecture provides a brief discussion of drugs which act as antagonists or inhibitors. Read pages 180-181.
The effects of drugs on the brain will be further discussed in Chapter 17.
Throughout the course you will continue to explore the physiological mechanics of behavior. In Lesson 3, the
theories of Sigmund Freud and B.F. Skinner on personality and behavior will be discussed.
Summarizing Your Learning

After reading "Asymmetry of Higher Function of the Cerebral Cortex," go to the PsychSim5 Web site.
Once there, select Hemispheric Specialization. You can review at your own pace by selecting the
NEXT button to the right of the screen.

Then, go to the PsychSim5 Web site. Once there, select Your Mind on Drugs. You can review at your
own pace by selecting the NEXT button to the right of the screen.