Unit 2: Biological Bases of Behavior
What makes you "you"? This question gets to the heart of one of the longest-running debates in psychology: the nurture versus nature dispute, which asks whether humans are a product of their environment or of their biological makeup. While it is unlikely that we will ever conclusively answer this question, research has provided us with some important insights that will help you understand the arguments on both sides of the debate.
Early psychologists considered the brain a black box that controlled certain processes, although they did not know how to identify these processes or how the brain controlled them. This is no longer the case; now, scientists insist that the psychological mind and physiological body are fully integrated with one another. Today, knowledge of the biological origins of our psychological states is integral to the study of psychology.
In this unit, we explore biopsychology, which includes the role of genes, the structure and functions of neurons, the parts of the nervous system, and the endocrine system. Finally, we examine the role and function of sleep and the use of substances that may alter our states of consciousness.
Completing this unit should take you approximately 7 hours.
Upon successful completion of this unit, you will be able to:
- discuss the role of genetics in human psychology and gene-environment interactions;
- explain the structure and function of neurons, neural communication, the brain, the spinal cord, the central nervous system, the peripheral nervous system, and the physiological and behavioral effects of neurotransmitters and psychoactive drugs;
- describe how researchers study and examine the brain and its functions, the behavioral effects of brain injuries, and the significance of split-brain operations;
- describe the endocrine system and the role of hormones in regulating body functions;
- describe the stages of sleep (REM and NREM) and their importance in proper psychological function, common sleep problems and disorders, and hypnosis; and
- explain how substance use disorders are classified by differentiating among major drug categories (stimulants, depressants, antipsychotics, opioids, hallucinogens).
2.1: Biopsychology and Human Genetics
Although psychology is defined as a social science that studies behavior and mental processes, the fields of genetics and biology are also important for explaining these phenomena. Specifically, we draw on these fields to understand the biological causes of behaviors and the significance of brain functions and development.
This text explores how genes and evolution affect behavior, explains the difference between genotype (our genetic makeup) and phenotypes (how our genes are expressed in appearance and behavior), and discusses the importance of gene-environment interactions.
The theory of evolution by natural selection requires the variability of a given trait. Why is variability necessary, and where does it come from?
Twin and adoption studies provide an opportunity to understand the role genes and the environment play in determining behaviors. Watch this video, which explains how scientists conduct these studies and how these comparisons help us answer questions.
Read this text on the risk factors for developing schizophrenia. There are important genetic contributions to the likelihood that someone will develop schizophrenia, with consistent evidence from family, twin, and adoption studies.
2.2: Cells of the Nervous System
The human brain is comprised of billions of specialized cells called neurons. In this section, we learn about the basic parts of a neuron, how neurons communicate with each other, and how drugs can mimic or interfere with normal neuronal communication.
Read this text. Cocaine has two effects on synaptic transmission: it impairs the reuptake of dopamine and causes more dopamine to be released into the synapse. Should we classify cocaine as an agonist or antagonist? Why?
Drugs such as lidocaine and novocaine act as Na+ channel blockers. In other words, they prevent sodium from moving across the neuronal membrane. Why does this effect make these drugs such effective local anesthetics?
Watch this video on the anatomy of a neuron. Pay attention to what a neuron looks like and how a neuron transmits signals. Think about how many signals are transmitted at any given time. Human beings are made up of very complex programming!
Watch this video on the action potential mechanism, which is essential for neural communication.
Watch this video, which explains the types of neurotransmitters and how they excite or inhibit neurons. Some common neurotransmitters are acetylcholine, norepinephrine, dopamine, serotonin, and gamma-aminobutyric acid (GABA). Acetylcholine and norepinephrine are excitatory neurotransmitters, while dopamine, serotonin, and GABA are inhibitory.
Watch this video, which expands on the type, structure, and function of neurotransmitters.
2.3: Parts of the Nervous System
Let's explore the two main divisions of the nervous system: the central nervous system and the peripheral nervous system. There are two main divisions within the peripheral nervous system: the somatic nervous system and the autonomic nervous system. Each of these divisions plays an important role in behavior and mental processes.
As you read this text, pay attention to the implications of compromised immune function due to exposure to chronic stress. Be sure to study Figure 3.14, which illustrates the effects of sympathetic nervous system activation. How do all of these components affect the fight or flight response?
The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body. Watch this video to understand how, together, these organs are responsible for the control of the body and communication among its parts.
2.4: The Brain and Spinal Cord
The central nervous system consists of the brain – which consists of two hemispheres, each containing four lobes – and the spinal cord. The following resources explain the functions of the spinal cord, describe the two hemispheres and how they are connected, and the functions of the four lobes. The first text wraps up with a discussion of the technologies that allow for direct observation of the brain's structures and functions.
Before the advent of modern imaging techniques, scientists and clinicians relied on autopsies of people who suffered brain injuries that caused behavioral changes to determine how different areas of the brain were affected. As you read this text, pay attention to the limitations associated with this kind of approach. Which of the techniques offers viable options for determining how activity in the reticular formation is related to sleep and wakefulness? Why?
Watch this video on phantom limb pain to understand how sensory neurons transmit information. This condition can affect people who have had an amputation.
As you read this article, pay attention to the video on split-brain operations. Test your knowledge by describing a split-brain patient and at least two important aspects of brain function these patients reveal.
2.5: The Endocrine System
The endocrine system controls hormone levels, which regulate a number of behaviors such as metabolism, growth, sexual functions, sleep, reproduction, and mood. Here we explore the major glands of the endocrine system, the hormones they each use, and the hormone's role in bodily functions.
Hormone secretion is often regulated through a negative feedback mechanism, which means that once a hormone is secreted, it will cause the hypothalamus and pituitary to shut down the production of signals necessary to secrete the hormone in the first place. Most oral contraceptives are made of small doses of estrogen or progesterone. Why is this an effective means of contraception?
Read this text. The nervous and endocrine systems both use chemical messengers. What properties do these two systems share? What properties are different? Which one is faster? Which one results in long-lasting changes?
Watch this video on the endocrine system and familiarize yourself with the major glands and hormones.
2.6: What Is Consciousness?
We use the word consciousness in many different contexts. For example, we might say someone loses consciousness or displays self-consciousness. But what does the word consciousness really mean in these different statements? In this section, we explore the meaning of consciousness, how our circadian rhythms work, and what we mean by sleep debt.
Read this text. Humans are generally considered diurnal, which means we are awake during the day and sleep at night. However, many rodents are nocturnal. Why do you think different animals have such different sleep-wake cycles?
If the theories that claim sleep is necessary to restore and recover from daily energetic demands are true, what is the relationship between an individual's total sleep duration and their level of activity? Why is it problematic for healthcare professionals to rotate their work shifts? What should hospitals do to alleviate potential problems?
We often see evidence of circadian rhythms when we travel across time zones. Watch this video for some sound strategies for reducing the effects of jet lag (disrupted circadian rhythms when traveling by jet).
2.7: Sleep and Why We Sleep
Sleep is a daily period of time and state of consciousness when the nervous system is relaxed and relatively inactive. Research has concluded that sleep is essential to our everyday health and functioning; even a short time without sleep can be linked to changes in our mood, awareness, and overall psychological functioning.
Read this text, which describes the brain areas that are involved in sleep, explains the hormones that are secreted during sleep, and provides several theories that attempt to explain the purpose of sleep.
How do researchers determine whether certain areas of the brain are involved in the regulation of sleep? Make sure you can differentiate the evolutionary theories of sleep and make a case for the one with the most compelling evidence.
2.8: Stages of Sleep
Before the 1950s, we assumed we spent all of our time during a night's sleep in a consistent level of unconsciousness. Thanks to pioneering research, we now know that sleep is cyclical and consists of four stages of non-REM sleep plus REM sleep.
Read this text, which explains the difference between REM and non-REM sleep, the characteristics of the four stages of non-REM sleep, and the role each type and stage play in learning and memory. Hint: Plan to get a good night's sleep after studying this section, so you will be sure to remember it!
Sigmund Freud (1856–1939), the Austrian neurologist and founder of psychoanalysis, believed that dreams give us insight into our unconscious mind. The content of our dreams provides clues into our unconscious. What are some criticisms of this perspective? Some people claim we act out our dreams during sleepwalking and talking in our sleep. Why does the text suggest this theory is unlikely?
2.9: Sleep Problems and Disorders
Many people struggle with sleep, either temporarily or chronically. In this section, we examine the symptoms and risk factors for the typical sleep disorders of insomnia, parasomnias, sleep apnea, sudden infant death syndrome (SIDS), and narcolepsy. We explore some treatment options for each of these afflictions.
Read this text. Therapists often suggest that people who suffer from insomnia should spend less time doing activities if they are awake in bed. Why do you think spending time awake in bed might interfere with our ability to fall asleep? How is narcolepsy with cataplexy similar to and different from REM sleep?
2.10: Substance Use and Abuse
Psychoactive drugs, such as prescription drugs and illegal substances, can induce altered states of consciousness. In this section, we explore the diagnostic criteria for substance use disorders, the neurotransmitter systems affected by different categories of psychoactive drugs, and how behaviors and mental processes are affected by different categories of drugs.
Read this text. The negative health consequences of alcohol and tobacco products are well-documented. However, many consider a drug like marijuana to be safe, if not safer, than legal drugs.
Why do you think marijuana use continues to be illegal in many parts of the United States? Why is it still important to develop tobacco cessation programs in addition to educating people about the dangers of using tobacco products?
This video explains substance use disorders as chronic medical conditions, the stigma surrounding substance use disorder, and treatment approaches.
Review this page which describes the acute effects and the health risks of both legal and illegal drugs.
Read this page on drugs, their effects on the brain, and how psychological and physiological addictions form.
Read this text. If you are interested in learning more about the science of drugs, the brain, and behavior, we encourage you to explore the U.S. National Institute of Drug Abuse website for more information on addiction prevention, health, treatment, and recovery.
2.11: Other States of Consciousness
For those who are able to enter these states of mind, hypnosis and meditation can alter our state of consciousness. In this section, we define and differentiate hypnosis and meditation and explain their limitations and possibilities.
As you read this text, think about the advantages of researching the potential health benefits of hypnosis. What studies are most convincing regarding the effectiveness of using meditation to treat physical and mental disorders?
Unit 2 Assessment
- Receive a grade
Take this assessment to see how well you understood this unit.
- This assessment does not count towards your grade. It is just for practice!
- You will see the correct answers when you submit your answers. Use this to help you study for the final exam!
- You can take this assessment as many times as you want, whenever you want.