Myers' Psychology for AP Second Edition Unit 3: Biological Bases of Behavior 

Module 9: Biological Psychology and Neurotransmission 

Biology, Behavior, and Mind

• To generate an idea or to feel emotions, you need the body. Trying to think without a body is trying to walk without legs 
• The mind comes from the brain. Even though the heart is associate with love, it is actually the brain that falls for someone 
• In the 1800s Franz Gall started phrenology. He believed that the different bumps on a person's skull could teach us about their mental abilities
• Although phrenology did not take off, it started the idea that different areas of the brain have different functions 
• Humans are biopsychosocial systems. We are made up of systems that have subsystems and those subsystems have subsystems 

Neural Communication 

• The operation systems of humans are very similar to that of other animals
• Scientists study animals, such as slugs, to understand how the basics work

Neurons: 

• The building blocks of the body's information system are neurons. Neurons can also be referred to as never cells 
• Neurons consist of a cell body and branching fibers. Dendrite fibers listen and receive information. Axon fibers speak and pass the messages on to other neurons, muscles, or glands.
• Dendrites are often short 
• Axons are very long. They can even spread several feet 
• Myelin sheaths encase axons. This fatty tissue speeds up the impulses 
• Neurons transmit messages when they are stimulated by are senses. They also transmit messages when they receive signals from other neurons 
• Neurons fire impulses which are called action potential 
• Impulses range in speed. Some go as slow as 2 miles per hour while others get up to 180
• Neurons generate electricity because ions are exchanged 
• Axons have resting potential. This means they have positive outsides and negative insides. The surface of an axon is selectively permeable because only certain things can pass through 
• When a neuron fires, the axon channels act like dominos. Each one opening after the next
• The pause after a neuron is fired is called the refractory period 
• Most signals are excitatory and try to push the neuron's accelerator 
• Others are inhibitory and try to push the breaks of the neuron 
• If there are more excitatory signals then inhibitory, then there is an action potential 
• A neuron's reaction is an all-or-nothing response. Meaning it will either fire or won't

How Neurons Communicate: 

• Even under a microscope, it is very hard to determine where one neuron ends and the next begins
• The meeting point between neurons is called the synapse 
• The gap between neurons, the synaptic gap, is less than 1 millionth of an inch wide 
• When action potential reaches the end of an axon, it triggers a neurotransmitter. The neurotransmitters then cross the synaptic gap and then bind to the receiving neuron 

How Neurotransmitters Influence Us: 

• There are dozens of neurotransmitters that influence hunger, thinking, depression, and other emotions 
• A particular brain pathway can only use one or two neurotransmitters at a time
• Neurotransmitters interact with other things in the body and their effects depend on what receptors they stimulate
• The acetylcholine (ACh) is a neurotransmitter that plays a role in learning and memory. The ACh is also the messenger between motor neurons and skeletal muscles. When ACh is released to the muscles, the muscles will contract 
• Research has been done to show the effects of morphine on the human brain. It is found that humans create their own version of morphine, endorphins, to respond to pain  

How Drugs and Other Chemicals Alter Neurotransmission:

• Once drugs are in the body for a long enough period, the brain stops producing its own natural opiates 
• Once a person stops taking a drug, they suffer from withdrawal. This is because the brain has suppressed making its own opiates and there are not enough in the body. This causes intense discomfort for the person 
• Agonists cause a person to get high and have pleasure because they are similar to neurotransmitters
• Antagonists block neurotransmitters from functioning 

Module 10: The Nervous and Endocrine Systems 

The Nervous System 

• The brain and the spinal cord form the central nervous system (CNS). This is the body's decision maker
• The peripheral nervous system (PNS) gathers information and transmits CNS decisions to the rest of the body 
• These two systems are what makes the nervous system 
• Nerves connect the CNS with muscles, glands, and sense organs 
• Information travels through the nervous system through three types of neurons; sensory, motor, and interneurons 
• Sensory neurons carry information from tissues and sensory receptors to the brain and spinal cord. Once they reach the brain they go through processing 
• Motor neurons carry instructions from the CNS to muscles and glands 
• Interneurons process the brain's internal communication system 

The Peripheral Nervous System: 

• The peripheral nervous system (PNS) is made up of the somatic nervous system and the autonomic nervous system
• The somatic nervous system enables voluntary control of the skeletal muscles 
• The autonomic nervous system controls glands and internal organs. This influences heartbeat and digestion 
• The autonomic nervous system usually operates on its own, but can be overridden if necessary   
• The sympathetic nervous system arouses and expends energy. This system can accelerate heartbeat, raise blood pressure, and make you alert 
• The sympathetic nervous system is usually in action when you sense danger or something alarms you 
• The parasympathetic nervous system conserves energy. It will decrease heartbeat and lower blood sugar 
• The parasympathetic nervous system usually works when you are calm 
• The sympathetic and parasympathetic nervous systems work together to keep the body at a steady state 

The Central Nervous System: 

• The brain enables our humanity. It is made up of billions and billions of neurons 
• The brain's neurons work in groups called neural networks. Neurons work with neurons that they have short and fast connections with 
• The spinal cord connects the peripheral nervous system with the brain 
• Ascending neural fibers send sensory information up 
• Descending neural fibers send motor-control information down 
• Reflexes are a cause of the spinal cord working 
• To produce pain or pleasure, information must reach the brain 

The Endocrine System 

• A second communication system is the endocrine system. This system secretes hormones into the bloodstream where they go on to affect other tissues
• Hormones can influence interest in sex, food, aggression, and more 
• Endocrine messages can take several seconds to reach the targeted tissue 
• The effects of endocrine messages often last longer than neural messages 
• The pituitary gland is the most important endocrine gland. Located in the center of the brain, this gland releases growth hormones and oxytocin. The pituitary can also influence how/when other glands release hormones 
• The nervous system directs the endocrine system which then affects the nervous system 

Module 11: Studying the Brain, and Older Brain Structures 

The Tools of Discovery Having Our Head Examined 

• Damage to one side of the brain often caused paralysis to the opposing body side. This lead scientists to conclude that the right side of the body is controlled by the left side of the brain. Likewise, the left side of the body is controlled by the right side of the brain 
• To conduct research, many scientists have created small lesions in the brain. Destroying small parts of the brain to see the effects. For example, destroying one part of the brain can change how much or how little we eat 
• Scientists have now discovered what areas of the brain do what. Meaning they can cause you to laugh or cry by activating certain neurons 
• Scientists use an electroencephalogram (EEG) to capture the electrical activity of the brain 
• Computed tomography (CT) scans can reveal brain damage 
• Positron emission tomography (PET) scans show the brain consuming glucose. This then shows researchers what areas of the brain are active when doing certain activities  
• Magnetic resonance imaging (MRI) scans provide detailed pictures of soft tissue 

Older Brain Structures 

• Animals with simpler brains include sharks. The brain regulates basic survival functions like eating and breathing but nothing else
• Animals like rodents have slightly more complex brains. They have emotion and greater memory 
• Advanced animals like humans have brains that process more information 

The Brainstem: 

• The brainstem is the oldest and innermost region 
• It begins where the spinal cord meets the brain
• The medulla is the base of the brainstem and controls heartbeat and breathing 
• Pons are right above the medulla and coordinate movement  
• The brainstem works as the crossover point. This is where the left side of the brain controls the right side of the body and vise versa 

The Thalamus: 

• The thalamus is located on top of the brainstem 
• It controls the brain's senses  
• It receives information from the sense, except smell, and routes the information to other areas of the brain 
• It can also receive the brain's replies. It would then send the messages to the medulla and cerebellum  

The Reticular Formation: 

• The reticular formation is inside the brainstem 
• It causes us to wake up 

The Cerebellum: 

• The cerebellum is located at the end of the brainstem 
• It is responsible for nonverbal learning and memory 
• It also controls time judgment and discriminating sounds 
• It also coordinates voluntary movement 

The Limbic System: 

• The cerebral hemispheres are the newest and highest parts of the brain 
• The area between old and new is called the limbic system 
• This system consists of the amygdala, hypothalamus, and hippocampus 
• The hippocampus processes memories we have while we are awake 

The Amygdala: 

• The amygdala is linked to aggression and fear 
• It controls the perception of these emotions as well as the processing of their memory 

The Hypothalamus: 

• The hypothalamus is located below the thalamus 
• It is a link to bodily maintenance 
• Neural clusters here influence hunger, thirst, body temperature, and sexual behavior 
• The hypothalamus monitors the state of your body. It then sends out hormones which go to other areas of the brain. Then these hormones cause that area to release some of their hormones 
• Some areas stimulate reward centers because they cause the brain to feel pleasure 

Module 12: The Cerebral Cortex 

Structure of the Cortex

• The cerebral cortex is a layer of interconnected neural cells 
• It consists of 23 billion nerve cells and 300 trillion synaptic connections 
• The left and right hemispheres of the brain have axons that connect the cortex with other areas of the brain 
• Glial cells provide nutrients and clean up after ions 
• The hemispheres cortex is broken up into four lobes 
• The frontal lobe is behind your forehead
• The parietal lobes are at the top of the head
• The occipital lobes are at the very back of the head
• The temporal lobes are closer to the middle 

Functions of the Cortex

Motor Functions: 

• The motor cortex is located at the back of the frontal lobes
• It controls movement to the opposite side of the body 

Mapping The Motor Cortex: 

• Areas that require precise control occupy the most cortical space 
• Scientists today can now predict what the motor cortex will do before a patient even moves 

Brain-Computer Interfaces: 

• Clinical trials of cognitive neural prosthetics are ongoing. Scientists put a chip into the motor cortex, allowing paralyzed people to use computers to complete tasks

Sensory Functions:

• The somatosensory cortex is located in the front of the parietal lobes 
• It specializes in receiving information from skin senses and from the movement of body parts 
• The more sensitive a body region, the more the somatosensory cortex is devoted to it 
• Visual information is being sent to the visual cortex. This is located in the occipital lobes 
• The auditory cortex processes anything you hear. It is located in the temporal lobes 

Association Areas: 

• The association areas are filled with neurons that work on higher mental functions 
• These areas interpret and act on sensory information. They then link it with memories 
• Association areas are found in all four lobes 
• The prefrontal cortex is in the frontal lobe. It allows for judgment, planning, and processing new memories. If this area gets damaged, a person can still complete tasks, but they would not be able to plan ahead
• Damaging the frontal lobe can also change your personality. Your moral compass is often broken and you can become less compassionate 
• The parietal lobe enable mathematical and spatial reasoning 
• The association area in the right temporal lobe allows us to recognize faces 
• Functions are not found in just one area. They are connected through many different parts of the brain 

The Brain's Plasticity 

• Plasticity is the brain's ability to modify itself after it has been damaged 
• Brain damage had lasting effects because severed neurons do not regenerate and some brain functions seem preassigned to specific areas
• On the bright side, some of the brain's neural tissue is able to reorganize in response to damage 
• Constraint-induced therapy tries to rewire the brain in order to help those with brain damage. Patients are forced to use their bad limb rather than their fully functioning one. This causes the brain to gradually reprogram 
• Damaged brain functions migrated to other brain regions, allowing full movement to the limbs once more 
• Those who are blind or deaf have unused brain areas. These areas get put into other uses. For example, in a blind person, their visual cortex is often rewired to increase their sense of touch 
• Neurogenesis is the process of forming new brain cells. This processes has been found in mice, birds, monkeys, and a few humans  

Module 13: Brain Hemisphere Organizations and the Biology of Consciousness 

Our Divided Brain 

• The left and right brain serve different functions 
• Damage to the left brain hurts reading, writing, speaking, reasoning, and understanding 
• Damage to the right brain also has effects, but they are less severe 

Splitting the Brain: 

• The corpus callosum connects the right and left brain together 
• Scientists can cause patients to have split brain by removing the corpus callosum. Patients with split brain did seem normal. There was no change in their personality or intellect 
• The split brain surgery leaves people with two separate minds 
• Both hemispheres can understand and follow instructions
• When the right brain does something on its own, the left brain tries to rationalize it   

Right-Left Differences in the Intact Brain 

• When a person performs a perceptual task there is an increase of activity in the right hemisphere 
• When a person speaks activity increases in the left hemisphere 
• Language is language even if it is not spoken. Deaf people use the left part of their brain to understand sign language 
• The right hemisphere makes inferences, modifies our speech so that it is clear, and helps orchestrate self sense 

The Biology of Consciousness 

• Consciousness helps with long-term interests 
• It also promotes survival by allowing us to read others. If you see an angry person your conscious will tell you to not make them any angrier 

Cognitive Neuroscience: 

• Cognitive neuroscientists study how brain activity is linked with mental processes 
• Even when a body is motionless, the brain and mind are still active 
• Many cognitive neuroscientists are working on exploring and mapping the conscious functions in the cortex 
• However, much is still to be learned about the mind. Scientists know what it does but they are still trying to figure out how it works 

Dual Processing The Two-Track Mind: 

• Cognitive neuroscience research can tell us what region of the brain becomes active with different conscious experiences 
• Scientists believe that there are two "levels" in the brain. They believe that most of the work is being done unconsciously. They consider conscious thinking the "high road" and unconscious thinking the "low road" 
• Although we tend to thinking vision is a single system, there are actually many regions of the brain that deal with vision. For example, a patient who has blindsight cannot see. But when they are put in a hallway filled with objects they are able to walk through it without bumping into anything. 
• Consciousness allows us to have voluntary control and communicate with others 
• Sometimes consciousness is not fast 
• An example of dull processing is walking to class while talking with your friend. You are consciously talking and listening while not paying attention to where you are walking. Yet you end up walking to your next class without even thinking about it 
• Unconscious activity can be overridden with conscious thought 

Module 14: Behavior Genetics Predicting Individual Differences 

Genes Our Codes for Life 

• Behavior geneticists study our differences. The take into account both our heredity and environment 
• Every cell nucleus in your body contains the genetic master code for your whole entire body 
• A human has 23 pairs of chromosomes, 46 in total. 23 of these come from your mother and the other half come from your father 
• Chromosomes are made up of DNA 
• Genes are small segments of DNA 
• Genes can be active, meaning they are expressed, or inactive 
• Small differences in DNA are what make us different from chimpanzees or bananas 
• Most traits, like height, face size, and intelligence, are all influenced by genes  

Twin and Adoption Studies 

Identical Versus Fraternal Twins:

• Identical twins come from a single egg that got split in two. Therefore they are genetically identical 
• Identical twins can differ in two ways. First, one twin may be more at risk for illnesses because they have less copies of certain genes. The second way is that one twin has a better placenta. Therefore they will have better nourishment, which can cause physical differences between the twins 
• Fraternal twins develop from two separate eggs. They are not genetically identical but rather share the same amount as any other brother-sister combination 
• Having the same genes means many twins can share the same experiences. For example, if an identical twin has Alzheimer's, the other twin has a 60% chance of also having it. This number lowers to 30% in fraternal twins 
• Studies have found that identical twins are more similar in behavior than fraternal twins 
• Identical twins report being treated like the same person whereas fraternal twins feel like they are two separate people. 

Separated Twins: 

• The story of the Jim brothers is one of twins who were separated at birth and had no idea the other one existed 
• The University of Minnesota did various testing on them and found that, despite being separated for 38 years, they were very alike. The researchers found similarities in both physical abilities, looks, and personality 
• Separated identical twins had less similar personalities then twins who were with each other their whole lives 

Biological Versus Adoptive Relatives: 

• Researchers who study the adoption method break it into two groups. The first group is genetic relatives which are composed of biological parents and siblings. The other group is called environmental relatives who are the adoptive parents and siblings 
• Scientists try to determine if the child is more like their biological or adoptive families 
• Research finds that traits like agreeableness are more similar to that of the biological parents 
• Adoptive parents do influence the attitudes, values, manners, faith, and politics of their adopted children 

The New Frontier Molecular Genetics 

• Molecular genetics tries to identify specific genes that influence behavior 
• Heredity influences body weight, but there is no "obese gene." But there are some genes that influence how many calories are burned when you complete certain tasks  
• Genetic tests can reveal what people are at risks for certain diseases. They analyze DNA as well as the family history from the patient in order to prevent problems occuring in the future 

Heritability 

• Heritability is the extent to which different traits are attributed to genes. For instance, the heritability of intelligence is 50%. But this does not mean your specific intelligence is 50%. Yours could be more or it could be less. The environmental factors also play a role in why it could be more or less  
• The heritability of different traits can be mathematically estimated 
• It is not known what percentage of an individual's personality is inherited. Heritability focuses on a whole group rather than one person 

Gene-Environment Interaction 

• Some traits, like having two eyes, are the same no matter the environment. Other traits are adaptive depending on your environment. A person who lives in Alaska will have a better time dealing with cold conditions than a person from Florida
• Genes are self-regulating because they react to their surroundings
• Genes and experiences are both important. They are able to work together because of their constant interactions
• Epigenetics studies what molecular mechanisms are triggered in different environments 
• Environmental triggers can switch certain genes on and off 

Module 15: Evolutionary Psychology: Understanding Human Nature

Natural Selection and Adaptation 

• Traits that are selected and show reproductive advantages will prevail in the species 
• Over the course of time, nature has done this manipulation rather than someone in a lab 
• Mutations are genetic errors that can produce positive outcomes. For example, blue eyes were originally a genetic mutation 
• Mutations allow humans to adapt to their environments 

Evolutionary Success Helps Explain Similarities 

Our Genetic Legacy: 

• Behavioral and biological similarities come from the fact that humans share a human genome 
• Most genetic differences are within a population. For example, the people of an Icelandic town all look different. But if you compare that town to a town in Kenya, the two groups will share many similar traits 
• Over the course of history humans have done things that help future generations. Such as learning the hard way the leopards should not be touched 
• Humans often share moral instincts 

Evolutionary Psychology Today: 

• The second Darwinian revolution refers to using evolutionary principles in psychology 
• It raises many questions about how men and women are alike and different 

An Evolutionary Explanation of Human Sexuality 

• Both men and women have adapted in similar ways. They eat the same foods, avoid the same animals, and learn and remember very similarly
• Differences mostly come from adaptive behaviors related to reproduction 

Gender Differences in Sexuality: 

• Men tend to have more of a sex drive than women 
• Men often see a women's friendliness as sexual rather than just friendly. This, unfortunately, often causes men to misread signals (this explains rather than excuses their behavior) causing things like sexual harassment.  

Natural Selection and Mating Preferences: 

• Evolutionary psychologists look to natural selection to determine why men have more of an interest in sex than women 
• Research have found that it is because women can only carry one child at a time (this excludes women who have twins or more) while men can impregnate multiple women 
• Evolution shows that men are more attracted to healthy, fertile-appearing women. A younger woman suggests they have more years to have children than an older one 
• Women are attracted to men who are more mature, dominant, and seem like long term partners because they want someone who will stick around when the baby is born 

The Evolutionary Perspective on Human Sexuality:

• Humans pair off monogamously and get married because there is a higher chance of getting the woman pregnant and the man sticking around
• Men tend to be attracted to women with domestic skills while women are attracted to men who seem like they can provide 
• Societal values also play a role in what men and women want in a partner and relationship 
• Psychologists are still struggling to explain things like same-sex attraction and how it falls in place with the typical pattern 

Reflections on the Nature and Nurture

• Our unique gene composition is what creates are shared humanity and individual differences
• Through family and friend relationships we learn multiple ways to think and act. Initiating different parts of our nature is influenced by our nurture 
• Societies influence on us also contributes. For example, men are genetically more aggressive and society says they are supposed to be "macho." Combining these two aspects gives you an aggressive "macho" man. But if there was a different societal norm for men, they would still be aggressive but not to the same extent 
• In today's world, it is more accepted that both men and women can complete the same tasks and roles 
• People can overpower their genes and cultural norms. For example, a person can decide they don't want kids. This defies what their genes and most cultures tell them 
• We are products of nature and nurture of the past, but we are shaping the nature and nurture for future generations 
• Trying to understand the universe is a difficult task that is often mind boggling. And understanding certain parts often leads to more questions. But learning more and more can help us with everyday tasks and allows us to create a better future 

Vocabulary: 

Biological psychology- the scientific study of the links between biological (genetic, neural, hormonal) and psychological processes. (Some biological psychologists call themselves behavioral neuroscientists, neuropsychologists, behavior geneticists, physiological psychologists, or biopsychologists)

Neuron- a nerve cell; the basic building block of the nervous system

Dendrites- a neuron's bushy, branching extensions that receive messages and conduct impulses toward the cell body

Axon- the neuron extension that passes messages through its branches to other neurons of to muscles or glands

Myelin sheath- a fatty tissue layer segmentally encasing the axons of some neutrons; enables vastly greater transmission speed as neural impulses hop from one sausage-like node to the next 

Action potential- a neutral impulse; a brief electrical charge that travels down an axon 

Refractory period- a period of inactivity after a neuron had fired 

Threshold- the level of stimulation required to trigger a neural impulse 

All-or-none response- a neuron's reaction of either firing (with a full-strength response) or not firing 

Synapse- the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic gap or synaptic cleft

Neurotransmitters- chemical messengers that cross the synaptic gaps between neurons. When released by sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neutral impulse 

Reuptake- a neurotransmitter's reabsorption by the sending neuron 

Endorphins- "morphine within"---natural, opiate-like neurotransmitters linked to pain control and to pleasure 

Agonist- a molecule that, by binding to a receptor site, stimulates a response 

Antagonist- a molecule that, by binding to a receptor site, inhibits or blocks a response 

Nervous system- the body's speedy, electrochemical communication network, consisting of all the nerve cells of peripheral and central nervous systems 

Central nervous system (CNS)- the brain and spinal cord 

Peripheral nervous system (PNS)- the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body 

Nerves- bundled axons that form neural "cables" connecting the central nervous system with muscles, glands, and sense organs 

Sensory (afferent) neurons- neurons that carry incoming information from the sensory receptors to the brain and spinal cord 

Motor (efferent) neurons- neurons that carry outgoing information from the brain and spinal cord to the muscles and glands 

Interneurons- neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs 

Somatic nervous system- the division of the peripheral nervous system that controls the body's skeletal muscles. Also called the skeletal nervous system

Autonomic nervous system (ANS)- the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms 

Sympathetic nervous system- the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations 

Parasympathetic nervous system- the division of the autonomic nervous system that calms the boyd, conserving its energy 

Reflex- a simple, automatic response to a sensory stimulus, such as the knee-jerk response

Endocrine system- the body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream 

Hormones- chemical messengers that are manufactured by the endocrine glands travel through the bloodstream and affect other tissues 

Adrenal glands- a pair of endocrine glands that sit just above the kidneys and secrete hormones (epinephrine and norepinephrine) that help arouse the body in times of stress

Pituitary gland- the endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands 

Lesion- tissue destruction. A brain lesion is a naturally or experimentally caused destruction of brain tissue 

Electroencephalogram (EEG)- an amplified recording of the waves of electrical activity sweeping across the brain's surface. These waves are measured by electrodes placed on the scalp 

CT (computed tomography) scan- a series of X-ray photographs taken from different angles and combined by computer into a composite representation of a slice of the brain's structure (Also called a CAT scan) 

PET (positron emission tomography) scan- a visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task 

MRI (magnetic resonance imaging)- a technique that uses magnetic fields and radio waves to produce computer-generated images of soft tissue. MRI scans show brain anatomy 

fMRI (functional MRI) a technique for revealing blood flow and therefore, brain activity, by comparing successive MRI scans. fMRI scans show brain function as well as its structure 

Brainstem- the oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull; the brainstem is responsible for automatic survival functions

Medulla- the base of the brainstem; controls heartbeat and breathing 

Thalamus- the brain's sensory control center, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla 

Reticular formation- a nerve network that travels through the brainstem and thalamus and plays an important role in controlling arousal 

Cerebellum- the "little brain" at the rear of the brainstem; functions include processing sensory input, coordination movement output and balance, and enabling nonverbal learning and memory 

Limbic system- neural system (including the hippocampus, amygdala, and hypothalamus) located below the cerebral hemispheres; associated with emotions and drives 

Amygdala- two lima-bean-sized neural clusters in the limbic system; linked to emotion 

Hypothalamus- a neural structure lying below the thalamus; it directs several maintenance activities (eating, drinking, body temperatures), helps given the endocrine system via the pituitary gland, and is linked to emotion and reward 

Cerebral cortex- the intricate fabric of interconnected neural cells covering the cerebral hemispheres; the body's ultimate control and information-processing center 

Glial cells (glia)- cells in the nervous system that support, nourish, and protect neurons; they may also play a role in learning and thinking 

Frontal lobes- portion of the cerebral cortex lying just behind the forehead; involved in speaking and muscle movements and in making plans and judgments 

Parietal lobes- portion of the cerebral cortex lying at the top of the head and toward the rear; receives sensory input for touch and boyd position 

Occipital lobes- portion of the cerebral cortex lying at the back of the head; includes areas that receive information from the visual fields 

Temporal lobes- portion of the cerebral cortex lying roughly above the ears; includes the auditory areas, each receiving information primarily from the opposite ear

Motor cortex- an area at the rear of the frontal lobes that controls voluntary movements 

Somatosensory cortex- area at the front of the parietal lobes that registers and processes body touch and movement sensations 

Association areas- areas of the cerebral cortex that are not involved in primary motor or sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking 

Plasticity- the brain's ability to change, especially during childhood, by reorganizing after damage of by building new pathways based on experience 

Neurogenesis- the formation of new neurons 

Corpus callosum- the large band of neural fibers connecting the two brain hemispheres and carrying messages between them 

Split brain- a condition resulting from surgery that isolates the brain's two hemispheres by cutting the fibers (mainly those of the corpus callosum) connecting them 

Consciousness- our awareness of ourselves and our environment 

Cognitive neuroscience- the interdisciplinary study of the brain activity linked with cognition (including perception, thinking, memory, and language) 

Dual processing- the principle that information is often simultaneously processed on separate conscious and nonconscious tracks 

Behavior genetics- the study of the relative power and limits of genetic and environmental influences on behavior 

Environmental- every external influence, from prenatal nutrition to the people and things around us 

Chromosomes- threadlike structures made of DNA molecules that contain genes 

DNA (deoxyribonucleic acid)- a complex molecule containing the genetic information that makes up the chromosomes 

Genes- the biochemical units of heredity that make up the chromosomes; segments of DNA capable of synthesizing proteins 

Genomes- the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes 

Identical twins (monozygotic twins)- twins who develop from a single fertilized egg that splits in two, creating two genetically identical organisms 

Fraternal twins (dizygotic twins)- twins who develop from separate fertilized eggs. They are genetically no closer than brothers and sisters, but they share a fetal environment 

Molecular genetics- the subfield of biology that studies the molecular structure and function of genes 

Heritability- the proportion of variation among individuals that we can attribute to genes. The heritability of a trait may vary, depending on the range of populations and environments studied 

Interaction- the interplay that occurs when the effect of one factor (such as environment) depends on another factor (such as heredity) 

Epigenetics- the study of environmental influences on gene expression that occur without a DNA change 

Evolutionary psychology- the study of the evolution of behavior and the mind, using principles of natural selection 

Natural selection- the principle that, among the range of inherited trait variations, those contributing to reproduction and survival will most likely be passed on to succeeding generations 

Mutation- a random error in gene replication that leads to a change