The Biology of Mind. Preview

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1 CHAPTER 2 The Biology of Mind Preview Or nervos system plays a vital role in how we think, feel, and act. Nerons, the basic bilding blocks of the body s circitry, receive signals throgh their branching dendrites and cell bodies and transmit electrical implses down their axons. Chemical messengers called nerotransmitters traverse the tiny synaptic gap between nerons and pass on excitatory or inhibitory messages. The central nervos system consists of the brain and spinal cord. The peripheral nervos system consists of the somatic nervos system, which directs volntary movements and reflexes, and the atonomic nervos system, which controls the glands and mscles of or internal organs. Hormones released by endocrine glands affect other tisses, inclding the brain. The most inflential endocrine gland, the pititary gland, releases hormones that inflence growth, and its secretions also inflence the release of hormones by other glands. The nervos system directs endocrine secretions, which then affect the nervos system. The brain s increasing complexity arises from new brain systems bilt on top of old. Within the brainstem are the oldest regions, the medlla and the reticlar formation. The thalams sits atop the brainstem and the cerebellm extends from the rear. The limbic system incldes the amygdala, the hippocamps, and the hypothalams. The cerebral cortex, representing the highest level of brain development, is responsible for or most complex fnctions. Each hemisphere of the cerebral cortex has for geographical areas: the frontal, parietal, occipital, and temporal lobes. Althogh small, well-defined regions within these lobes control mscle movement and receive information from the body senses, most of the cortex its association areas are free to process other information. Experiments on split-brain patients sggest that, for most people, the left hemisphere is the more verbal and the right hemisphere excels in visal perception. Stdies of people with intact brains indicate that each hemisphere makes niqe contribtions to the integrated fnctions of the brain. Introdctory Exercise: Fact or Falsehood? The correct answers to Handot 2 1 are as follows: 1. F 2. T 3. T 4. T 5. F 6. F 7. T 8. F 9. T 10. T 15

2 16 Chapter 2 The Biology of Mind HANDOUT 2 1 Fact or Falsehood? 1. Neral implses travel throgh the hman body at the same speed that electricity travels throgh a wire. 2. The hman brain prodces its own natral opiates that elevate mood and ease pain. 3. Electrically stimlating a cat s brain at a certain point can case the animal to cower in terror in the presence of a small mose. 4. Both animals and hmans seem to have reward centers located in the brain. 5. We ordinarily se only 10 percent of or brains. 6. Most people wold advocate pshing someone in front of a rnaway boxcar to save five others. 7. If a blind person ses one finger to read Braille, the brain area dedicated to that finger expands. 8. Adlt hmans cannot generate new brain cells. 9. Some people have had the hemispheres of their brains split with no apparent ill effect. 10. Hearing people sally se the left hemisphere of the brain to process langage, and deaf people sally se the left hemisphere to process sign langage.

3 Chapter 2 The Biology of Mind 17 Gide Objectives Every qestion in the Test Banks is keyed to one of these objectives. Neral and Hormonal Systems 2-1. Explain why psychologists are concerned with hman biology Describe nerons, and explain how they transmit information Describe how nerve cells commnicate with other nerve cells Describe how nerotransmitters inflence behavior, and explain how drgs and other chemicals affect nerotransmission Describe the fnctions of the nervos system s main divisions, and identify the three main types of nerons Describe how the endocrine system transmits information and interacts with the nervos system. Tools of Discovery and Older Brain Strctres 2-7. Describe how neroscientists stdy the brain s connections to behavior and mind Describe the strctres that make p the brainstem, and smmarize the fnctions of the brainstem, thalams, reticlar formation, and cerebellm Describe the strctres and fnctions of the limbic system. The Cerebral Cortex and Or Divided Brain Describe the fnctions of the varios cerebral cortex regions Discss the extent to which a damaged brain can reorganize itself, and define nerogenesis Describe what split brains reveal abot the fnctions of or two brain hemispheres Describe what research tells s abot being left-handed, and discss whether it is advantageos to be righthanded. Neral and Hormonal Systems Biology, Behavior, and Mind Lectre: Phrenology 2-1. Explain why psychologists are concerned with hman biology. Everything psychological is simltaneosly biological. We think, feel, and act with or bodies. By stdying the links between biology and behavior, the biological perspective enables s to gain a better nderstanding of or experiences of sights and sonds, meanings and memories, pain and passion. In the 1800s, Franz Gall invented phrenology, a poplar theory that claimed that bmps on the skll reveal or mental abilities and or character traits. Althogh bmps on the skll reveal nothing abot the brain s nderlying fnctions, Gall was accrate in spposing that varios brain regions have particlar fnctions. Neral Commnication Lectre: Mltiple Sclerosis and Gillain-Barré Syndrome Exercise: Modeling a Neron PsychSim 6: Neral Messages LanchPad Video and Animation: The Neron: Basic Units of Commnication; Animation: Ion Flow At all levels, researchers examine how we take in information and then how we organize, interpret, store, and se it. The information systems of hmans and other animals operate similarly. This similarity permits researchers to stdy relatively simple animals to discover how or neral systems operate.

4 18 Chapter 2 The Biology of Mind 2-2. Describe nerons, and explain how they transmit information. A neron consists of a cell body and branching fibers: The dendrite fibers receive information from sensory receptors or other nerons, and the axon fibers pass that information along to other nerons. The axons of some nerons are encased by a myelin sheath, which helps speed their implses. A neral implse, or action potential, fires when the neron is stimlated by signals from the senses or when triggered by chemical signals from neighboring nerons. The action potential is a brief electrical charge that travels down the axon. Received signals trigger an implse only if the excitatory signals mins the inhibitory signals exceeds a minimm intensity called the threshold. The neron s reaction is an all-or-none response. Dring the resting potential, the flid interior of the axon carries mostly negatively charged atoms (ions), while the flid otside has mostly positively charged atoms. Then, the first bit of the axon is depolarized (its selectively permeable srface allows positive ions in), and the electrical implse travels down the axon as channels open, admitting ions with a positive charge. Dring a resting pase (the refractory period), the neron pmps the positively charged sodim ions back otside. Then it can fire again. Exercises: Neral Transmission; Crossing the Synaptic Gap; Reaction-Time Measre of Neral Transmission and Mental Processes Demonstration: The Action Potential LanchPad Videos and Animations: Neral Commnication: Implse Transmission Across the Synapse; Animation: Signal Transmission; Synaptic Activity 2-3. Describe how nerve cells commnicate with other nerve cells. When electrical implses reach the axon terminal, they stimlate the release of chemical messengers called nerotransmitters that cross the jnction between nerons called the synapse. After these molecles traverse the tiny synaptic gap (cleft) between nerons, they bind to receptor sites on neighboring nerons, ths passing on their excitatory or inhibitory messages. Excess nerotransmitters are reabsorbed, in a process called reptake, drift away, or are broken down by enzymes. Lectre: Endorphins and Nerostimlation LanchPad Videos: Chemically Indced Hallcinations: Stdies of Anesthetic Drgs; Parkinson s Disease: A Case Stdy 2-4. Describe how nerotransmitters inflence behavior, and explain how drgs and other chemicals affect nerotransmission. Different nerotransmitters have different effects on behavior and emotion. For example, the nerotransmitter acetylcholine (ACh) plays a crcial role in learning and memory. Fond at every jnction between a motor neron and skeletal mscle, ACh cases the mscle to contract. The brain s endorphins, natral opiates released in response to pain and vigoros exercise, explain the rnner s high and the indifference to pain in some injred people. When the brain is flooded with opiate drgs sch as heroin and morphine, it may stop prodcing its own natral opiates, and withdrawal of these drgs may reslt in intense discomfort ntil the brain resmes prodction of its natral opiates. Some drgs and other chemicals are agonists; they increase a nerotransmitter s action, either by increasing the prodction or release of the nerotransmitters or blocking reptake in the synapse. Or, they may be similar enogh to a nerotransmitter to bind to its receptor and mimic its effect. Some opiate drgs are agonists. Other drgs or chemicals are antagonists; they decrease a nerotransmitter s action by blocking prodction or release. Botlin, a poison that can form in improperly canned food, cases paralysis by blocking ACh release.

5 Chapter 2 The Biology of Mind 19 The Nervos System Lectres: Lo Gehrig s Disease; The Atonomic Nervos System and Sexal Fnctioning; The Sympathetic Nervos System and the Polygraph; The Sympathetic Nervos System and Performance Exercise: Drg Effects and the Nervos System LanchPad Video: The Central Nervos System: Spotlight on the Brain 2-5. Describe the fnctions of the nervos system s main divisions, and identify the three main types of nerons. Nerons commnicating with other nerons form or body s primary system, the nervos system. The brain and spinal cord form the central nervos system (CNS). The peripheral nervos system (PNS) links the central nervos system with the body s sense receptors, mscles, and glands. The axons carrying this PNS information are bndled into the electrical cables we know as nerves. Sensory nerons send information from the body s tisses and sensory organs inward to the brain and spinal cord, which process the information. Motor nerons carry otgoing information from the central nervos system to the body s tisses. Internerons in the central nervos system commnicate internally and intervene between the sensory inpts and the motor otpts. The somatic nervos system of the peripheral nervos system enables volntary control of or skeletal mscles. The atonomic nervos system of the peripheral nervos system is a dal selfreglating system that inflences the glands and mscles of or internal organs. The sympathetic nervos system aroses; the parasympathetic nervos system calms. The brain s nerons clster into work grops called neral networks. The cells in each layer of a neral network interrelate with varios cells in the next layer. Learning occrs as feedback strengthens the work grops. Reflexes, which are simple, atomatic responses to stimli, illstrate the spinal cord s work. A simple reflex pathway is composed of a single sensory neron and a single motor neron, which often commnicate throgh an interneron. For example, when or fingers toch a candle s flame, information from the skin receptors travels inward via a sensory neron to a spinal cord interneron, which sends a signal otward to the arm mscles via a motor neron. Becase this reflex involves only the spinal cord, we jerk or hand away before the brain creates an experience of pain. The Endocrine System Lectres: The Endocrine System; Oxytocin: The Hormone of Love, Bonding, and Generosity? 2-6. Describe how the endocrine system transmits information and interacts with the nervos system. The endocrine system s glands secrete hormones, chemical messengers prodced in one tisse that travel throgh the bloodstream and affect other tisses, inclding the brain. Compared with the speed at which messages move throgh the nervos system, endocrine messages move more slowly, bt their effects sally last longer. The endocrine system s hormones inflence many aspects of or lives, inclding growth, reprodction, metabolism, and mood, keeping everything in balance while responding to stress, exertion, and internal thoghts. In a moment of danger, the adrenal glands release the hormones epinephrine and norepinephrine, which increase heart rate, blood pressre, and blood sgar, providing s with increased energy. The pititary gland is the endocrine system s most inflential gland. Under the inflence of the brain s hypothalams, the pititary s secretions inflence growth and the release of hormones by other endocrine glands. These may in trn inflence both the brain and behavior and ths reveal the intimate connection of the nervos and endocrine systems.

6 20 Chapter 2 The Biology of Mind Tools of Discovery and Older Brain Strctres The Tools of Discovery: Having Or Head Examined Lectres: Neroimaging Techniqes; Assessing Awareness in Brain-Injred Patients; Concssions in Sports; Brain Pzzles, Models, and Molds Exercises: Bilding a Play-Doh Brain; A Portable Brain Model; Mastering Brain Strctre; Case Stdies in Neroanatomy; Neropsychology of Zombies Project: Color the Brain PsychSim 6: Brain and Behavior; Brain Treasre Hnt LanchPad Videos and Animations: Neroimaging: Assessing What s Cool; Mapping the Brain Throgh Electrical Stimlation; Event-Related Potential (ERP) Research; Animation: Neroimaging Techniqes; Animation: Fnctional Imaging Techniqes 2-7. Describe how neroscientists stdy the brain s connections to behavior and mind. The oldest method of stdying the brain involved observing the effects of brain diseases and injries. Powerfl new techniqes now reveal brain strctres and activities in the living brain. By srgically lesioning and electrically stimlating specific brain areas, by recording electrical activity on the brain s srface (electroencephalogram [EEG]), and by looking inside the living brain to see its activity (PET, MRI, and fmri), neroscientists examine the connections between brain, mind, and behavior. Older Brain Strctres Lectre: Conjoined Twins and a Shared Thalams; Why Can t We Tickle Orselves? Exercise: Individal Differences in Physiological Fnctioning and Behavior 2-8. Describe the strctres that make p the brainstem, and smmarize the fnctions of the brainstem, thalams, reticlar formation, and cerebellm. The brainstem, the brain s oldest and innermost region, is responsible for atomatic srvival fnctions. It incldes the medlla, which controls heartbeat and breathing, and the reticlar formation, which plays an important role in controlling arosal. Jst above the medlla is the pons, which helps coordinate movement and control sleep. Atop the brainstem is the thalams, the brain s sensory switchboard. It receives information from all the senses, except smell, and sends it to the higher brain regions that deal with seeing, hearing, tasting, and toching. The cerebellm, which is attached to the rear of the brainstem (along with the basal ganglia, deep brain strctres involved in motor movement) enables nonverbal learning and skill memory. It also helps s jdge time, modlate or emotions, and discriminate sonds and textres. Lectres: The Case of Clive Wearing; H.M. s Brain LanchPad Videos: Complsive Gambling and the Brain s Pleasre Center; Self-Stimlation in Rats 2-9. Describe the strctres and fnctions of the limbic system. The limbic system has been linked primarily to memory, emotions, and drives. For example, one of its neral centers, the hippocamps, processes conscios memory. Another, the amygdala, inflences aggression and fear. A third, the hypothalams, has been linked to varios bodily maintenance fnctions and to pleasrable rewards. Its hormones inflence the pititary gland, and ths it provides a major link between the nervos and endocrine systems.

7 Chapter 2 The Biology of Mind 21 The Cerebral Cortex and Or Divided Brain The Cerebral Cortex Lectres: Einstein s Brain and Genis; Kim Peek s Brain Exercises: Neroscience and Moral Jdgments; The Sensory Homncls LanchPad Videos and Animations: Planning, Life Goals, and the Frontal Lobe; Brain and Behavior: Phineas Gage Revisited; Animation: Sensory Motor Cortex Describe the fnctions of the varios cerebral cortex regions. The cerebral cortex, a thin srface layer of interconnected neral cells, is or body s ltimate control and information-processing center. Glial cells spport, norish, and protect the nerve cells of the cerebral cortex. The frontal lobes, jst behind the forehead, are involved in speaking, mscle movements, and planning and making jdgments. The parietal lobes, at the top of head and toward the rear, receive sensory inpt for toch and body position. The occipital lobes, at the back of the head, inclde visal areas. The temporal lobes, jst above the ears, inclde aditory areas. Each lobe performs many fnctions and interacts with other areas of the cortex. The motor cortex, an arch-shaped region at the rear of the frontal lobes, controls volntary mscle movements on the opposite side of the body. Body parts reqiring the most precise control occpy the greatest amont of cortical space. In an effort to find the sorce of motor control, researchers have recorded messages from brain areas involved in planning and intention, leading to the testing of cognitive neral prosthetics for paralyzed patients. This brain-compter interface may one day reslt in hmans being able to control machines with their thoghts. The sensory cortex, a region at the front of the parietal lobes, registers and processes body sensations. The most sensitive body parts reqire the largest amont of space in the sensory cortex. The association areas are not involved in primary motor or sensory fnctions. Rather, they integrate and act on information processed by the sensory areas. They are involved in higher mental fnctions, sch as learning, remembering, thinking, and speaking. Association areas are fond in all for lobes. Complex hman abilities, sch as memory and langage, reslt from the intricate coordination of many brain areas. Lectre: Hemispherectomy LanchPad Videos: Langage and Brain Plasticity; Brain Plasticity: Rewiring the Visal Cortex; Achieving Hemispheric Balance: Improving Sports Performance; Experience and Exercise: Generating New Brain Cells Discss the extent to which a damaged brain can reorganize itself, and define nerogenesis. Research indicates that some neral tisse can reorganize in response to damage. When one brain area is damaged, others may in time take over some of its fnction. For example, if yo lose a finger, the sensory cortex that received its inpt will begin to receive inpt from the adjacent fingers, which become more sensitive. Or brains are most plastic when we are yong children. Constraint-indced therapy rewires the brain by restraining a flly fnctioning limb and forcing se of the bad hand or the ncooperative leg. Eventally, the therapy reprograms the brain, improving the dexterity of a brain-damaged child or even an adlt stroke victim. New evidence reveals that adlt hmans can also generate new brain cells. Monkey brains illstrate nerogenesis by forming thosands of new nerons each day.

8 22 Chapter 2 The Biology of Mind Or Divided Brain Lectre: The Wada Sodim Amobarbital Test Exercise: Behavioral Effects of the Split-Brain Operation Project/Exercise: Hemispheric Specialization LanchPad Videos and Animation: The Split Brain: Lessons on Langage, Vision, and Free Will; The Split Brain: Lessons on Cognition and the Cerebral Hemispheres; Animation: Split Brain Fnctioning PsychSim 6: Hemispheric Specialization Describe what split brains reveal abot the fnctions of or two brain hemispheres. A split brain is one in which the corps callosm, the wide band of axon fibers that connects the two brain hemispheres, has been severed. Experiments on split-brain patients have refined or knowledge of each hemisphere s special fnctions (called lateralization). In the laboratory, investigators ask a split-brain patient to look at a designated spot, then send information to either the left or right hemisphere (by flashing it to the right or left visal field). Qizzing each hemisphere separately, the researchers have confirmed that for most people, the left hemisphere is the more verbal and the right hemisphere excels in visal perception. Stdies of people with intact brains have confirmed that the right and left hemispheres each make niqe contribtions. For example, the left hemisphere makes qick, literal interpretations of langage, and the right hemisphere excels in making inferences Describe what research tells s abot being left-handed, and discss whether it is advantageos to be right-handed. Abot 10 percent of s are left-handed. Almost all right-handers process speech primarily in the left hemisphere. Left-handers are more diverse. Seven in 10 process speech in the left hemisphere and the rest either process speech in the right hemisphere or se both hemispheres. Left-handers are more nmeros among those with reading disabilities, allergies, and migraine headaches. Lefthandedness is also more common among msicians, mathematicians, professional baseball and cricket players, architects, and artists. The advantages and disadvantages of being a lefty seem roghly eqal. Roger Sperry sees the mind and brain as a holistic system: The brain creates and controls the emergent mind, which in trn inflences the brain.