2.2 Biology and Behavior: Studying the Last Frontier
Imagine that you lost a sizable chunk of your brain. How would it impact your life? Would you be the same person as before? Your brain houses your thoughts, emotions, and personality, and orchestrates your behavior. It files away all your memories and dark secrets, and is involved in your every move, from the beat of your heart to the blink of your eye.
However, the human brain is only one part of the most complex living entity known. The human nervous system is a communication network that conveys messages throughout your body, using electrical and chemical processes. The nervous system contains the brain, spinal cord, and other nerves and fibers, and includes some 100 billion (1011) nerve cells. For a sense of what that number represents, consider that, in 2013, the population of the United States was approximately 314 million people; the number of nerve cells is approximately 333 times the number of people living in the United States. These cells are interlinked through some 100 quadrillion (1015) connections (Tang, Nyengaard, De Groot, & Gundersen, 2001). This intricate, ever-adapting web of connections gives us the power to think and feel in ways that are different from—and vastly more complex than—the thinking and feeling capacities of other organisms.
LO 1 Define neuroscience and explain its contributions to our understanding of behavior.
Consider the many tasks your brain is juggling at this very moment. As you scan the words on this page, your brain helps control the tiny muscles moving your eyes back and forth as well as the larger muscles in your neck and torso that keep you sitting upright. Light-sensitive cells in the back of your eyes relay signals, using electricity and chemicals, to various brain regions that transform the black marks on this page into words, sentences, and ideas for you to remember. And all the while, your brain is processing nonvisual sensory input such as sounds and smells, working with other nerve cells in your body to make sure your heart keeps pumping, your lungs keep breathing, and your glands and organs keep releasing hormones properly.
51
Neuroscience
CONNECTIONS
In Chapter 1, we presented the four major goals of psychology, which are to describe, explain, predict, and control behavior. These four goals guide psychologists’ investigations of how biology influences behavior. As you read through this chapter, try to keep these goals in mind.
Brandon’s injury resulted in a significant loss of his brain tissue. Remarkably, not only did he survive, but he can still talk about what occurred, think about the events, and feel emotions regarding what happened to him. How exactly does his brain orchestrate all these complex functions, especially after severe trauma? And how does a noninjured brain carry out these complicated processes? Scientists have developed a decent understanding of how individual brain cells communicate with each other, but they have yet to provide definitive answers to “big questions” involving the brain and other parts of the nervous system such as: How do we think? What is consciousness? Why must we sleep? This is why the brain may be regarded as the last frontier of medicine. Neuroscience, the study of the brain and nervous system, actually extends far beyond the borders of medicine and into disciplines as diverse as engineering, computer science, and our personal favorite—psychology. The subfield of psychology concerned with understanding how the brain and other biological systems influence human behavior is called biological psychology, which brings us to the goal of this chapter: to examine how biology influences our behavior.
52
In the pages to come, we will discuss some exciting new research findings and technologies used in neuroscience, but first we must get down to the basics: an examination of the nervous system, and how its various components work together to create sensations, movement, thoughts, and emotions. Our chapter-long “learning tour” of the nervous system will begin in the microscopic world of nerve cells, or neurons. Neurons are specialized cells that communicate with each other through both electrical and chemical signals. They are the building blocks of the brain, spinal cord, and nerves.
THE AWAKENING
Two weeks after the shooting, Brandon finally awoke from his coma. He could not move or feel the right side of his body, and he had lost the ability to use language. There were so many things he wanted to say to his family, but when he opened his mouth, the only sound that came out was “ugh.” Weeks went by before Brandon uttered his first word: “no.” That was all he could say for months, even when he was dying to say “yes.” During Brandon’s recovery, for example, his parents asked if he wanted some pizza, but all he could spit out was the word “no” (while nodding his head “yes”), even though he craved a hot, dripping slice like never before.
Apart from the paralysis to his right side and his difficulty with language, Brandon’s other abilities seemed fine. He could remember people, places, and objects, and he reported no trouble hearing, smelling, or tasting (The pizza tasted so good when he finally got it!). Although Brandon was not as outgoing and self-assured as before, he hadn’t changed much overall.
Why did the trauma to Brandon’s brain cause deficits in language, but not memory? Why was the right side of his body paralyzed, while the left side worked fine? Our discussion of the brain’s organization later in this chapter will clear up these mysteries for you. But first, let’s find out how neurons communicate.
show what you know
Question 2.1
1. Comprised of the brain, spinal cord, and other nerves, is a __________ communication network that conveys messages throughout the body, using electrical and chemical processes.
- consciousness
- the human nervous system
- a neuron
- the skull
Question 2.2
2. A researcher studying the impact of Brandon’s brain injury might work in the field of __________, which includes the study of the brain and nervous system.
Question 2.3
3. In the next section, you will learn much more about neurons, which are often referred to as the “building blocks” of the nervous system. What building blocks are you familiar with in other fields of study?
CHECK YOUR ANSWERS IN APPENDIX C.