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Psychological Science, 3rd Edition Michael Gazzaniga Todd Heatherton Diane Halpern Biological Foundations 3 Questions to Consider: What Is the Genetic Basis of Psychological Science? How Does the Nervous System Operate? What Are the Basic Brain Structures and Their Functions? How Are Neural Messages Integrated into Communication Systems? How Does the Brain Change? What Is the Genetic Basis of Psychological Science? Heredity Involves Passing Along Genes through Reproduction Genotypic Variation Is Created by Sexual Reproduction Genes Affect Behavior Social and Environmental Contexts Influence Genetic Expression Genetic Expression Can Be Modified Critical Thinking Skill: Seeking Disconfirming Evidence Learning Objective Explain how genes transmit information between generations in ways that can affect behaviors and emotions. What Is the Genetic Basis of Psychological Science? Genetics = Inheritance and Gene Expression Chromosomes are made of genes Genes are segments of DNA Genes provide instructions for making proteins Status of “The Human Genome Project” Each cell in the human body includes pairs of chromosomes, which consist of DNA strands. DNA has a double helix shape and is composed of genes. The 23rd chromosome pair determines sex: A female has two X chromosomes in that pair, whereas a male has one X and one Y. Heredity Involves Passing Along Genes through Reproduction Genes’ variations are either dominant or recessive The genome represents the genotype, and the observable characteristics are the phenotype Many characteristics are polygenic Mendel’s experiments with cross-breeding pea blossoms resulted in purple flowers 75 percent of the time and white flowers 25 percent of the time. Genotypic Variation Is Created by Sexual Reproduction Half of each chromosome comes from each parent and the two halves are joined randomly There is enormous potential variation in the resulting zygote’s genome Mutations also give rise to variations Genes Affect Behavior Behavioral genetics methods Twin studies, research on adoptees, and other investigations of hereditary and genetic influence provide insight into heritability Heritability Behavioral geneticists can quantify the similarity and variation in a population’s shared characteristics A )Fraternal twins, such as this pair pictured during their 13th birthday party, result when two separate eggs are fertilized at the same time. b) Identical twins result when one fertilized egg splits in two. Identical twins Gerald Levey and Mark Newman, participants in Dr. Bouchard’s study, were separated at birth. Reunited at age 31, they discovered they were both firefighters and had similar personality traits. Social and Environmental Contexts Influence Genetic Expression Genes guide development of characteristics Final expression of genes is a complex interaction between genetic makeup and environmental context Genetic Expression Can Be Modified Genetic manipulation has been achieved in mammals such as mice Difficult in humans Animal studies using the technique of “knocking out” genes to determine their effects on behaviors and on disease are a valuable tool for understanding genetic influences Critical Thinking Skill Seeking disconfirming evidence We focus on information that confirms what we already believe Creating a table comparing evidence from both sides can prevent us from ignoring disconfirming evidence How Does the Nervous System Operate? Neurons Are Specialized for Communication Action Potentials Cause Neural Communication Neurotransmitters Bind to Receptors across the Synapse Neurotransmitters Influence Mind and Behavior Learning Objectives Describe the electrical and chemical bases for communication among neurons. List the major neurotransmitters and what they do. Neurons Are Specialized for Communication Neurons are the basic building blocks of the nervous system They receive and send chemical messages All neurons have the same structure, but neurons vary by function and by location in the nervous system Neurons Are Specialized for Communication Types of neurons Sensory neurons Motor neurons Interneurons Receptors send afferent signals to the brain for processing. An efferent signal is then sent from the brain to the body via the spinal cord to produce a response. Messages are received by the dendrites, processed in the cell body, transmitted along the axon, and sent to other neurons via chemical substances released from the terminal buttons across the synapse. Neurons Are Specialized for Communication Resting membrane potential When a neuron is resting, the inside and outside differ electrically Sodium and potassium ions contribute to a neuron’s resting membrane potential A neuron at rest is polarized—it has a different electrical charge inside and outside. The passage of negative and positive ions inside and outside the membrane is regulated by ion channels located at the nodes of Ranvier. Action Potentials Cause Neural Communication Changes in a neuron’s electrical charge result in an action potential, or neural firing Signals are excitatory or inhibitory The electrical charge inside the neuron starts out slightly negative (resting membrane potential). As the neuron fires, it allows more positive ions inside the cell (depolarization). Through natural restoration (repolarization), it then returns to its slightly negative resting state. Action Potentials Cause Neural Communication Firing is the means of communication within networks of neurons The all-or-none principle Neuron fires with the same potency every time How often it fires depends on the strength of stimulation Neurotransmitters Bind to Receptors across the Synapse Neurons do not touch They release chemicals (neurotransmitters) into the synapse, a small gap between the neurons Neurotransmitters bind with the receptors of postsynaptic neurons, thus changing the charge in those neurons Neurotransmitters Bind to Receptors across the Synapse Reuptake Neurotransmitters’ effects are halted by reuptake of the neurotransmitters into the presynaptic neurons The cycle of reuptake and release repeats continuously Neurotransmitters Influence Mind and Behavior More than 60 neurotransmitters that influence aspects of the mind and of behavior in humans have been identified Including emotions, motor skills, sleep, learning and memory, pain control, and pain perception Neurotransmitters Influence Mind and Behavior Drugs and toxins can alter neurotransmitters actions in several ways Drugs that enhance neurotransmitters’ action are agonists Drugs that inhibit these actions are antagonists In this way, these substances can influence how we think and feel What Are the Basic Brain Structures and Their Functions? The Brainstem Houses the Basic Programs of Survival The Cerebellum Is Essential for Movement Subcortical Structures Control Emotions and Basic Drives The Cerebral Cortex Underlies Complex Mental Activity Learning Objectives Identify the basic structures in the brain and their primary functions. What Are the Basic Brain Structures and Their Functions? The nervous system’s different parts all have essential roles The central nervous system (CNS) Spinal cord and the brain The peripheral nervous system (PNS) All the other nerve cells in the body What Are the Basic Brain Structures and Their Functions? Psychological scientists have learned a great deal about the different brain regions through studying people with damaged brains Phineas Gage Franz Gall and his Phrenology Broca’s area Lesion in anterior association area: Changes in personality, unable to manage the life (homeless drifter), deficits in long-term planning and judgment. This illustration shows the location of Broca’s area. The Brainstem Houses the Basic Programs of Survival At the base of the skull, the top of the spinal cord forms the brainstem, which is involved in basic functions such as breathing and walking as well as general arousal The Cerebellum Is Essential for Movement The cerebellum (“little brain”), the bulging structure connected to the back of the brainstem, controls balance and is essential for movement Subcortical Structures Control Emotions and Basic Drives The subcortical structures play a key part in psychological functions Hypothalamus Controls vital functions Thalamus Sensory relay Subcortical Structures Control Emotions and Basic Drives Hippocampus Amygdala Memories Emotions Basal ganglia Planning and producing of movement The Cerebral Cortex Underlies Complex Mental Activity The lobes of the cortex each play specific roles Occipital Vision Parietal Touch The Cerebral Cortex Underlies Complex Mental Activity Temporal hearing and speech comprehension Frontal Planning and movement The cortical representation of the body surface is organized in strips that run down the side of the brain. Connected areas of the body tend to be represented next to each other in the cortex, and more sensitive skin regions have more cortical area devoted to them. This drawing, made by a hemineglect patient, omits much of the flower’s left side. How Are Neural Messages Integrated into Communication Systems? The Peripheral Nervous System Includes the Somatic and Autonomic Systems The Endocrine System Communicates through Hormones Actions of the Nervous System and Endocrine System Are Coordinated Learning Objectives Describe the key structures in the endocrine system and how they communicate to affect behavior. The PNS Includes the Somatic and Autonomic Systems Autonomic system The structures and functions that regulate the body’s internal environment Divided into the alarm response (sympathetic) and the return-to-normal response (parasympathetic) Somatic system Relays sensory information The Endocrine System Communicates through Hormones Both endocrine glands and organs produce and release chemical substances Travel to body tissues through the bloodstream and influence a variety of processes, including sexual behavior Actions of the Nervous System and Endocrine System Are Coordinated The endocrine system is controlled by the central nervous system Most of the central control of the endocrine system occurs through the actions of both the hypothalamus and the pituitary gland Pituitary gland controls the release of hormones from the rest of the endocrine glands How Does the Brain Change? The Interplay of Genes and Environment Wires the Brain Culture Affects the Brain The Brain Rewires Itself throughout Life Critical Thinking Skill: Recognizing Unstated Assumptions Females’ and Males’ Brains Are Similar and Different The Brain Can Recover from Injury Learning Objectives Explain how culture and other environmental factors change the brain. Describe the similarities and differences in females’ and males’ brains and explain the limitations on what we can infer from sex differences in the brain. The Interplay of Genes and Environment Wires the Brain Chemical signals influence the growth and function of cells Environmental experiences, especially during critical periods, are necessary for cells to develop properly and for them to make more detailed connections Culture Affects the Brain Daily social interactions, which vary among cultures (and subcultures and individuals), are reflected each in brain’s unique organization The Brain Rewires Itself throughout Life Although plasticity decreases with age, the brain retains the ability to rewire itself throughout life This ability is learning’s biological basis The Brain Rewires Itself throughout Life Change in the strength of connections between neurons underlies learning Fire together, wire together The functions of portions of the cerebral cortex shift in response to activity Phantom limb The participant felt a cotton swab touching his cheek as touching his missing hand. This effect may occur because the hand and face are near each other in somatosensory space. The Brain Rewires Itself throughout Life The puzzle of synesthesia Cross-sensory experience is called synesthesia Example: some people taste words or hear colors Synesthesia is genetic Critical Thinking Skill Recognizing unstated assumptions All human interactions are based partly on assumptions When trying to understand a complex topic, recognize unstated assumptions so that you can apply reason to them Females’ and Males’ Brains Are Similar and Different Sex differences in the brain reflect biological and environmental effects Males’ and females’ brains are predominantly similar Females’ and Males’ Brains Are Similar and Different Differences in males’ and females’ brains: Males’ brains are larger than females’ (on average) Females’ verbal abilities are organized more bilaterally (more equally in both hemispheres) Females’ brains have a greater proportion of gray matter, while males’ brains have a greater proportion of white matter Females’ and Males’ Brains Are Similar and Different There is no basis for deciding that either sex has the “better” brain The sexes’ differences in information processing arise from environmental experiences and genetic propensities A considerable body of evidence indicates that female brains are more bilaterally organized for language. For example, researchers at Indiana University studied men and women listening to someone reading aloud. As these fMRI images show, the men listened with one side of their brains, whereas the women tended to listen with both sides. The Brain Can Recover from Injury The brain can reorganize its functions in response to brain damage This capacity decreases with age Transplanted stem cells may be able to grow to replace damaged neurons The Brain Can Recover from Injury Anomalies in sensation and in perception, such as synesthesia, are attributed to crosswiring connections in the brain