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I understand that neurotransmitters are used to send signals between neurons in the brain and that some are used for rather specific functions. However, is the exact distribution/concentration/consumption and tolerances of neurotransmitters in various areas of the brain known?
Related and considered:
Which neurotransmitters can be measured in a living human brain?
Neurotransmitter based imaging techniques
The Science of Healing Thoughts
For centuries, the idea of &ldquohealing thoughts&rdquo has held sway over the faithful. In recent decades it&rsquos fascinated the followers of all manner of self-help movements, including those whose main purpose seems to be separating the sick from their money. Now, though, a growing body of scientific research suggests that our mind can play an important role in healing our body &mdash or in staying healthy in the first place. In the book Cure, the veteran science journalist Jo Marchant brings her critical eye to this fascinating new terrain, sharing the latest discoveries and telling the stories of the people &mdashIraq war veterans among them &mdash who are being helped by cures aimed at both body and mind. Marchant answered questions from Mind Matters editor Gareth Cook.
You have taken on a topic where, historically, there has been a tremendous amount of quackery. What convinced you that there was a compelling scientific story to tell?
The misunderstandings and false claims were one of the elements that drew me to the topic of mind-body medicine in the first place. The mind influences physiology in many ways &mdash from stress to sexual arousal &mdash so it has always seemed reasonable to me that it might impact health. Yet the question has become so polarized: advocates of alternative medicine claim miracle cures, while many conventional scientists and doctors insist any suggestion of &ldquohealing thoughts&rdquo is deluded.
I was interested in those clashing philosophies: I wanted to look at why it is so difficult to have a reasoned debate about this issue. What drives so many people to believe in the pseudoscientific claims of alternative therapists, and why are skeptics so resistant to any suggestion that the mind might influence health?
At the same time, I wanted to dig through the scientific research to find out what the evidence really says about the mind&rsquos effects on the body. That took me around the world, interviewing scientists who are investigating this question (often struggling for funding or risking their reputations to do so) and their results persuaded me that as well as being an interesting sociological or philosophical story, this was a compelling scientific one.
Examples include trials demonstrating that hypnotherapy is a highly effective treatment for patients with irritable bowel syndrome (IBS), and studies showing that perceived stress correlates with telomere length in cells. But what I personally found most convincing were studies suggesting an evolutionary rationale for the mind&rsquos influence on health.
There are now several lines of research suggesting that our mental perception of the world constantly informs and guides our immune system in a way that makes us better able to respond to future threats. That was a sort of &lsquoaha&rsquo moment for me &mdash where the idea of an entwined mind and body suddenly made more scientific sense than an ephemeral consciousness that&rsquos somehow separated from our physical selves.
What is known about what the placebo effect actually is, and what do you see as the biggest open questions?
&ldquoPlacebo effect&rdquo can be a confusing term, because it has several different meanings. It is sometimes used to cover anyone who feels better after receiving placebo (or fake) treatment, which of course includes all those people who would have improved anyway. But researchers are finding that taking a placebo can also have specific, measurable effects on the brain and body.
As neuroscientist Fabrizio Benedetti, one of the pioneers of placebo research, puts it, there isn&rsquot just one placebo effect but many. Placebo painkillers can trigger the release of natural pain-relieving chemicals called endorphins. Patients with Parkinson&rsquos disease respond to placebos with a flood of dopamine. Fake oxygen, given to someone at altitude, has been shown to cut levels of neurotransmitters called prostaglandins (which dilate blood vessels, among other things, and are responsible for many of the symptoms of altitude sickness).
None of these biological effects are caused by placebos themselves, which are by definition inert. They are triggered by our psychological response to those fake treatments. The active ingredients are complex and not fully understood but include our expectation that we will feel better (which in turn is affected by all sorts of factors such as our previous experience with treatment, how impressive or invasive a treatment is, and whether we&rsquore an optimistic person) and feeling listened to and cared for.
Another element is conditioning, where if we learn to associate a particular treatment &mdash taking a pill, say &mdash with a certain biological response, we experience that response when we take a similar pill in the future, even if it&rsquos a placebo. This influences physiological functions such as hormone levels and immune responses, and works regardless of our conscious beliefs.
Future questions include teasing out the psychological factors that shape placebo responses, and investigating why honest placebos (where someone knows they are taking a placebo) seem to work &mdash this research has barely begun. Scientists also want to pin down exactly what conditions placebos work for (most research so far is on a few model systems, like pain, depression and Parkinson&rsquos), and who they work for (both genes and personality seem to play a role). And then of course there is the question of how we can maximize these responses, and integrate them into routine clinical care in an honest way.
Have you experienced any of these mind-over-body effects yourself?
I took a placebo pill that I ordered online and it did get rid of a bad headache within about 20 minutes, but of course that&rsquos not a scientific trial. Perhaps my headache would have faded anyway. I also experienced the value of social support when giving birth to my two children. I had dramatically different outcomes when supported by midwives I knew and trusted, compared to a series of strangers. Again, my case doesn&rsquot prove anything on its own but this effect is borne out in trials with thousands of women: continuous one-on-one support during labor is one of the only known interventions that reduces the risk of surgery during childbirth.
Mostly though, I experienced the effects I describe in the book through talking to people treated using some of these approaches, often participants in clinical trials. They included a kidney transplant patient drinking a lavender-flavored milk to calm his hostile immune system people who have suffered decades of recurrent depression now kept well by mindfulness training and pilgrims seeking healing at the religious sanctuary of Lourdes in France. Meeting these people took this beyond an intellectual project for me. They showed me how the scientific findings aren&rsquot just statistics on the page but have the power to transform lives.
You write about burn victims who are being treated, in part, with virtual reality. Can you explain this, and what lessons you think it holds?
This is another therapy I got to try &mdash researchers in Seattle have developed a virtual reality landscape called Snow World. You fly around inside an ice canyon and fire snowballs at characters inside the game, such as penguins and snowmen. It&rsquos meant to work as a painkiller: the idea is that the brain has a limited capacity for attention, so if the ice canyon commands that attention, there is less capacity left over for experiencing pain. When I tried Snow World, the researchers used a heated box to simulate a burn to my foot &ndash it was quite painful outside the game, but once immersed, I had so much fun I barely noticed it.
This technique was developed to help burn victims &mdash they have to undergo agonizing sessions of wound treatment and physiotherapy. Even when taking the maximum safe dose of painkillers these patients are often still left in horrible pain. Trials show that undergoing these sessions while immersed in Snow World reduces their pain by an extra 15-40% on top of the relief they get from drugs.
This is just one of many lines of research telling us that the brain plays a big role in determining the level of pain we feel. Of course any physical damage is important, but it is neither sufficient nor necessary for us to feel pain. So I think we&rsquove got our approach to pain all wrong. Our focus is almost exclusively on trying to banish it with drugs, which is incredibly costly and causes huge problems with side effects and addiction. Research like Snow World shows the potential of psychological approaches for treating pain: both to maximize the effectiveness of drugs and perhaps in some cases to replace them.
Are you a scientist who specializes in neuroscience, cognitive science, or psychology? And have you read a recent peer-reviewed paper that you would like to write about? Please send suggestions to Mind Matters editor Gareth Cook. Gareth, a Pulitzer prize-winning journalist, is the series editor of Best American Infographics and can be reached at garethideas AT gmail.com or Twitter @garethideas.
ABOUT THE AUTHOR(S)
Gareth Cook is a Pulitzer Prize–winning journalist who edits Scientific American's Mind Matters online news column.
An Integrative Theory of Prefrontal Cortex Function
Earl K. Miller Jonathan D. Cohen
Vol. 24, 2001
▪ Abstract The prefrontal cortex has long been suspected to play an important role in cognitive control, in the ability to orchestrate thought and action in accordance with internal goals. Its neural basis, however, has remained a mystery. Here, we . Read More
Figure 1: Schematic diagram of some of the extrinsic and intrinsic connections of the prefrontal cortex. The partial convergence of inputs from many brain systems and internal connections of the pref.
Figure 2: Schematic diagram illustrating our suggested role for the PF cortex in cognitive control. Shown are processing units representing cues such as sensory inputs, current motivational state, me.
Figure 3: (A) Shown is the activity of four single prefrontal (PF) neurons when each of two objects, on different trials, instructed either a saccade to the right or a saccade to the left. The lines .
Figure 4: Schematic of the Stroop model. Circles represent processing units, corresponding to a population of neurons assumed to code a given piece of information. Lines represent connections between.
Figure 5: Time course of fMRI activity in dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC) during two phases of a trial in the instructed Stroop task. During the instruction.
Your Thoughts Can Release Abilities Beyond Normal Limits
There seems to be a simple way to instantly increase a person&rsquos level of general knowledge. Psychologists Ulrich Weger and Stephen Loughnan recently asked two groups of people to answer questions. People in one group were told that before each question, the answer would be briefly flashed on their screens &mdash too quickly to consciously perceive, but slow enough for their unconscious to take it in. The other group was told that the flashes simply signaled the next question. In fact, for both groups, a random string of letters, not the answers, was flashed. But, remarkably, the people who thought the answers were flashed did better on the test. Expecting to know the answers made people more likely to get the answers right.
Our cognitive and physical abilities are in general limited, but our conceptions of the nature and extent of those limits may need revising. In many cases, thinking that we are limited is itself a limiting factor. There is accumulating evidence that suggests that our thoughts are often capable of extending our cognitive and physical limits.
Can our thoughts improve our vision? We tend to believe that an essentially mechanical process determines how well we see. Recent research by Ellen Langer and colleagues suggests otherwise. It is a common belief that fighter pilots have very good vision. The researchers put people in the mindset of an Air Force pilot by bringing them into a flight simulator. The simulator consisted of an actual cockpit including flight instruments. The cockpit was mounted on hydraulic lifts that mimic aircraft movement and performance. People were given green army fatigues they sat in the pilot&rsquos seat, and performed simple flight maneuvers. They took a vision test while &ldquoflying&rdquo the simulator. A control group took the same vision test in the cockpit while the simulator was inactive. People&rsquos vision improved only if they were in the working simulator.
To rule out the possible effect of motivation, the researchers brought another group of people into the cockpit and asked them to read a brief essay on motivation. After people finished reading, they were strongly urged to be as motivated as possible and try hard to perform well in the vision test. The test was conducted while the simulator was inactive. They did not show a significant improvement.
In an eye exam, we are used to start experiencing problems at the bottom third of the eye chart, where letters start to get small. In another experiment, Ellen Langer and colleagues showed people a shifted chart. At the top, it included letters equivalent to the medium-size letters on the normal eye chart and the chart progressed to letters of very small size at the bottom. Because people were expecting to read the top two thirds of the shifted chart as well, they were able to read much smaller letters.
We also tend to think that our bodies respond to physical exercise in a mechanical way. We count our calorie intake, the calories we lose on a treadmill, etc. However, merely changing our thoughts about our physical activity seems capable of changing our bodies. Hotel room attendants clean on average 15 rooms per day, each room taking between 20 and 30 minutes to complete. (The physical activity involved meets the Surgeon General&rsquos recommendation of at least 30 minutes of physical exercise per day for a healthy lifestyle.) However, most hotel room attendants believe that they do not get regular exercise and a lot of them believe that they do not get any exercise at all. Alia Crum and Ellen Langer told hotel room attendants that their work provided the recommended exercise for a healthy lifestyle. This treatment group was monitored for 4 weeks. A control group of hotel room attendants, who were not told that their work provided the recommended exercise, was similarly monitored. People in the treatment group lost weight their body fat percentages, waist-to-hip ratios, and systolic blood pressures dropped. People in the control group showed no such improvement. These changes occurred despite the fact that the hotel room attendants&rsquo amount of work, amount of exercise outside of work, and diets stayed the same.
Recent research on placebos gives us clues about the mechanisms by which our mental activity causes these effects. In a conceptual replication of earlier work, Antonella Pollo and colleagues asked people to lift a certain amount of weight before and after drinking caffeine at high doses. The liquid in fact contained no caffeine, but the weight was secretly reduced after people drank it. That way, people learned to associate the liquid with less fatigue. Later, when people lifted the original weight after drinking the liquid, they experienced less fatigue. It seems that a central neural governor of fatigue suppressed the fatigue response. Marion Goebel and colleagues gave allergic patients allergy medication after a novel-tasting liquid. Later, drinking the liquid with fake medication suppressed the immune system and allergic skin reactions. Fabrizio Benedetti and colleagues first increased people&rsquos growth hormone levels by injecting medication. Later, injecting a saline solution (salt and water) presented as medication resulted in similar increases in hormone levels. Predrag Petrovic and colleagues suppressed people&rsquos emotional reactions to unpleasant pictures by injecting antianxiety medication. Later, injecting a saline solution presented as medication resulted in reduced activation in brain areas associated with anxiety.
Expectancies, such as expecting that one&rsquos work will bring about health benefits, are capable of producing physiological outcomes. Learned associations, such as the association between being an Air Force pilot and having good vision, can alter other cognitive processes, such as visual perception. Meanwhile, placebo effects observed in clinical research work via expectancies and learned associations created by fake operations, sham drugs, etc. Such expectancies and learned associations have been shown to change the chemistry and circuitry of the brain. These changes may result in such physiological and cognitive outcomes as less fatigue, less immune system reaction, elevated hormone levels, and less anxiety. The interventions that resulted in better performance in a knowledge test or better vision are placebos outside of the clinical context. However, the chemical and neural mechanisms by which they operate are probably similar.
These are likely manifestations of an adaptation that helped us survive throughout our evolutionary history by helping us prepare for the future. For example, when subtle cues in an environment trigger thoughts about a predator, that in turn triggers physiological changes that prepare the body for the impending confrontation even before the predator comes into sight.
If mindsets can change us, maybe we can deliberately choose our mindsets to improve our abilities. We can choose to adopt a mindset that improves creativity, for instance. People who think of categories as flexible and actively focus on the novel aspects of the environment become more creative. Ellen Langer and Alison Piper introduced people to familiar or unfamiliar objects conditionally or unconditionally. If an object, say a dog&rsquos chew toy, was introduced unconditionally, its description simply read, &ldquoThis is a dog&rsquos chew toy.&rdquo When the dog&rsquos chew toy was introduced conditionally, its description read, &ldquoThis could be a dog&rsquos chew toy.&rdquo When an object is introduced conditionally, it is categorized flexibly and it is easier to focus on the aspects of an unfamiliar object without preconceptions. When people were asked to solve a problem that required creative use of available objects, only people who were introduced conditionally to unfamiliar objects could solve the problem.
As this line of research advances, we will likely discover new ways of taking control of our mindsets. Weger and Loughnan, the researchers who improved people&rsquos knowledge test results with a bogus prime, wrote, &ldquoPeople have significant psychological resources to improve their well-being and performance, but these resources often go unused and could be better harnessed.&rdquo The mind and body are not separate our thoughts have remarkable control over our bodies and our mindsets are capable of improving our brains&rsquo performance.
Neuroscience is showing that the pathways of addiction are based in the brain. Using advanced techniques such as imaging methods and studies with animal models, researchers are learning more about how alcohol interacts with the brain’s communication system in different people. Innovative technology also is helping identify the changes that occur in the brain’s structure and function as a result of drinking, and how alcohol disrupts the brain’s delicate chemical balance. This information may help scientists understand why and how alcoholism develops in different populations and ultimately result in more effective and targeted therapies for alcohol abuse and dependence.
Introduction to Psychology
Copyright © 2015 by Achieve All rights reserved. This book or any portion thereof may not be reproduced or used in any manner whatsoever without the express written permission of the publisher except for the use of brief quotations in a book review. Printed in the United States of America First Printing, 2015 Achieve PO Box 10188 #29831 Newark, NJ 07101-3188 Tel: 888.900.8380 Visit the Achieve website for more information.
Introduction to Psychology
© 2015 of 97 Table of Contents Chapter One: The Nature and History of Psychology. 5 1.1 Definition and Goals of Psychology. 5 1.2 History of Psychology. 6 1.3 Research Methods. 9 1.4 Psychological Specialties. 13 Chapter 1 Practice Quiz. 15 Chapter Two: Biological Influences on Behavior. 16 2.1 Genes, Evolution, and Environment . 16 2.2 Environmental Influences . 18 2.3 Nervous System . 19 Chapter Two Practice Quiz . 26 Chapter Three: Sensation and Perception. 27 3.1 Psychophysics and Thresholds. 27 3.2 Sensory Adaptation . 27 3.3 Vision. 28 3.4 Hearing . 28 3.5 Taste . 29 3.6 Smell . 29 3.7 Skin Senses. 30 3.8 Basic Perceptual Phenomena . 30 3.9 Influences on Perception. 31 3.10 Subliminal Perception . 32 3.11 Extrasensory Perception . 32 Chapter Three Practice Quiz . 33 Chapter Four: Consciousness. 34 4.1 Biological Rhythms. 34 4.2 Sleep. 34 4.3 Hypnosis. 36 4.4 Psychoactive Drugs . 36 Chapter Four Practice Quiz. 38 Chapter Five: Learning and Memory . 39 5.1 Learning . 39 5.2 Memory . 42 Achieve Page 3
Introduction to Psychology of 97 5.3 Memory as a Reconstructive Process . 42 Chapter Five Practice Quiz. 45 Chapter Six: Motivation and Emotion. 46 6.1 Specific Motives . 46 Chapter Six Practice Quiz . 51 Chapter Seven: Thinking and Intelligence. 52 7.1 Cognition. 52 7.2 Intelligence. 54 Chapter Seven Practice Quiz . 57 Chapter Eight: Human Development . 58 8.1 Development over the Lifespan . 58 8.2 Early Development . 62 8.3 Influences of Gender Development. 63 Chapter Eight Practice Quiz. 65 Chapter Nine: Personality . 66 9.1 Theories of Personality. 66 Chapter Nine Practice Quiz. 72 Chapter Ten: Psychological Disorders and Therapies. 73 10.1 Abnormal Psychology . 73 10.2 Disorders. 76 10.3 Approaches to Therapy. 79 Chapter Ten Practice Quiz. 81 Chapter Eleven: Social Psychology . 82 11.1 Behavior in Social and Cultural Context. 82 11.2 Attitude . 84 11.3 Group Behavior . 85 Chapter Eleven Practice Quiz. 90 Practice Test. 91 True and False Questions . 95 Answer Keys. 96 © 2015 Achieve Page 4
Introduction to Psychology
Chapter One: The Nature and History of Psychology Learning Objectives After completing Unit One, you should be able to: 1. Describe and explain the definition and goal of psychology 2. Discuss the history of psychology 3. Discuss the different perspectives on behavior 4. Discuss the scientific principles of psychology 5. Discuss the different methods of research 6. Discuss the different specialties in psychology
1.1 Definition and Goals of Psychology Psychology is the scientific study of behavior and the mind. The term ‘behavior’ refers to actions and responses that we can directly observe, whereas the term ‘mind’ refers to internal states and processes, such as thoughts and feelings that cannot be seen directly and that must be inferred from observable, measurable responses. Psychology began as an attempt to answer philosophical questions about human nature, using methods borrowed from physics, physiology, and other sciences. Psychology’s systematic approach yields more accurate knowledge about behavior than do every day casual observations and conventional folk wisdom, which have generated many misconceptions and myths about human nature. As a science, psychology has four central goals: description, explanation, control, and application. • Description is the most basic goal. Psychologists seek to describe how people behave, think, and feel. • Explanation typically takes the form of hypotheses and theories which specify the causes of behavior, as psychologists strive to explain and to understand why people act as they do. • Control is where psychologists design experiments or other types of research to test the accuracy of their proposed explanations. • Application is where psychologists apply psychological knowledge in ways that enhance human welfare. Science involves both basic research, which reflects the quest for knowledge for its own sake, and applied research, which focuses on solving practical problems. For psychologists, most research examines how and why people behave, think, and feel the way they do.
Introduction to Psychology
© 2015 of 97 1.2 History of Psychology Humans have long sought to understand themselves, and for ages, the mind-body problem has occupied the center of this quest. Many early philosophers held a position of mind-body dualism, the belief that the mind is a spiritual entity not subject to physical laws that govern the body. Dualism implies that no amount of research on the physical body, including the brain, could ever hope to unravel the mysteries of the nonphysical mind. Another view is that of monism, which holds that the mind and body are one and that the mind is not a separate spiritual entity. To monists, mental events correspond to physical events in the brain. Monism helped set the stage for psychology because it implied that the mind could be studied by measuring physical processes within the brain. Discoveries in physiology (an area of biology that examines bodily functioning) and medicine helped pave the way for psychology’s emergence. Several major perspectives have shaped psychology’s scientific growth. Structuralism and Wundt The infant science of psychology emerged in 1879, when Wilhelm Wundt established the first experimental psychology laboratory at the University of Leipzig in Germany. He believed that the mind could be studied by breaking it down into basic components, as a chemist might break down a complex chemical compound. This approach came to be known as structuralism, which is the analysis of the mind in terms of its basic elements. In their experiments, structuralists used the method of introspection (looking within) to study sensations and reporting on one’s own conscious thoughts and feelings, which they considered the basic elements of consciousness. Structuralism left an important mark by establishing a scientific tradition for studying cognitive processes. Functionalism and James In the United States, structuralism eventually gave way to functionalism, which held that psychology should study the functions of consciousness rather than its elements. Functionalism was influenced by Darwin’s evolutionary theory, which stressed the importance of adaptation in helping organisms survive and reproduce in their environment. William James, a leader in the functionalist movement, taught courses in physiology and psychology at Harvard University. James helped widen the scope of psychology to include the study of various biological and mental processes and overt behavior. Although functionalism no longer exists as a school of thought within psychology, its tradition endures in two modern-day fields: cognitive psychology, which studies mental processes, and evolutionary psychology, which emphasizes the adaptiveness of behavior. Achieve Page 6
Introduction to Psychology
© 2015 of 97 Gestalt Psychology By the 1920s, German scientists had formed a school of thought known as Gestalt psychology, which examined how the mind organizes elements of experience into a unified or whole perception. They argued that perceptions are organized so that the whole is greater than the sum of its parts. Gestalt psychology stimulated interest in topics such as perception and problem solving. Pavlov and Classical Conditioning In the early 1900s, experiments by Russian physiologist Ivan Pavlov revealed how learning occurs when events are associated with one another. Pavlov found that dogs automatically learned to salivate to the sound of a new stimulus, such as a tone or bell, if that stimulus was repeatedly paired with a known stimulus, such as food. This particular type of psychology examines how organisms learn through the consequences of their actions. Thus, learning is the key to understanding how experience molds behavior. Watson, Skinner, and Behaviorism The behavioral perspective emphasizes how the external environment and learning shape behavior. Watson and Skinner believed that psychology should study only observable stimuli and responses, not unobservable mental processes. Behaviorism is a school of thought which emphasizes environmental control of behavior through learning. Behaviorists sought to discover laws that govern learning, and they believed that the same basic principles of learning applied to all organisms. Skinner was a leading 20th century behaviorist who believed that the real causes of behavior reside in the outer world: “A person does not act upon the world, the world acts upon him”. Skinner believed that through social engineering, society could harness the power of the environment to change behavior in beneficial ways. His approach, known as radical behaviorism, was esteemed for its scientific contributions and for focusing attention on how environmental forces could be used to enhance human welfare. Freud and the Psychodynamic Perspective The psychodynamic perspective searches for the causes of behavior within the inner workings of our personality (our unique pattern of traits, emotions, and motives), emphasizing the role of unconscious processes. Sigmund Freud developed the first and most influential psychodynamic theory. Freud was convinced that an unconscious part of the mind profoundly influences behavior, and he developed a theory and form of psychotherapy called psychoanalysis - the analysis of internal and primary unconscious psychological forces. Achieve Page 7
Introduction to Psychology of 97 Freud also proposed that humans have powerful inborn sexual and aggressive drives and that, because these desires are punished in childhood, we learn to fear them and become anxious when we are aware of their presence. This leads us to develop defense mechanisms, which are psychological techniques that help us cope with anxiety and the pain of traumatic experiences. Repression, a primary defense mechanism, protects us by keeping unacceptable impulses, feelings, and memories in the unconscious depths of the mind. All behavior, whether normal or abnormal, reflects a largely unconscious and inevitable conflict between the defenses and internal impulses. Humanistic Psychology The humanistic perspective emphasizes free will, personal growth, and the attempt to find meaning in one’s existence. The humanistic perspective emphasizes personal freedom and choice, personal growth, and self-actualization. Abraham Maslow was a humanistic theorist who proposed that each of us has an inborn force toward self-actualization, the reaching of one’s individual potential. When people develop in a supportive environment, their positive inner nature emerges. Biological Perspective The biological perspective examines how brain processes and other bodily functions regulate behavior and psychological characteristics. Behavioral neuroscientists study brain activity and hormonal influences behavior geneticists examine the role of heredity and evolutionary psychologists seek to explain how evolution has biologically predisposed modern humans toward certain ways of behaving. Evolutionary Psychology Evolutionary psychology seeks to explain how evolution shaped modern behavior. Evolutionary psychologists stress that human mental abilities and behavioral tendencies evolved along with a changing body. According to one theory, as our humanlike ancestors developed new physical abilities, they began to use tools and weapons and live in social groups. In his theory of evolution, Darwin noted that within a species some members possess specific traits to a greater extent than do other members. Through a process he called natural selection, if an inherited trait gives certain members an advantage over others, these members will be more likely to survive and pass these characteristics on to their offspring. In this way, species evolve as the presence of adaptive traits increases within the population over generations. Thus, through natural selection, adaptations to new environmental demands contributed to the development of the brain, just as the brain growth contributed to the further development of human behavior. © 2015 Achieve Page 8
Introduction to Psychology
© 2015 of 97 Cognitive Perspective The cognitive perspective, embodied by the subfield of cognitive psychology, views humans as information processors who think, judge, and solve problems. Cognitive neuroscience examines brain processes that occur as people perform mental tasks. This perspective views the human as a thinker, studying a person’s thoughts, anticipations, planning, perceptions, attention, and memory processes. Sociocultural Perspective The sociocultural perspective examines how the social environment and cultural learning influence our behavior and thoughts. Cultural psychologists study how culture is transmitted to members of society and examine similarities and differences among people from various cultures. This perspective studies the human as a social being embedded in a culture, and assesses social forces, including norms, social interactions, and group processes in one’s culture and social environment. 1.3 Research Methods Because psychology is a science, information about human behavior is collected in systematic, objective, and replicable ways - primarily through experimental and correlation studies. Whenever possible, scientists prefer to test their understanding of “what causes what” more directly. If we truly understand the causes of a given behavior, then we should be able to predict the conditions under which that behavior will occur in the future. Furthermore, if we can control those conditions, then we should be able to produce that behavior. Psychologists conduct research to gather evidence about behavior and its causes. The research method chosen depends on the problem being studied, the investigator’s objectives, and ethical principles. Case Study A case study is an in-depth analysis of an individual, a group, or event. By studying a single case in detail, researchers typically hope to discover principles that hold true for people or situations in general. Data may be gathered through observation, interviews, psychological tests, physiological recordings, or task performance. Case studies have several advantages and disadvantages: Advantages: • When a rare phenomenon occurs, this method enables scientists to study it closely. • A case study may challenge the validity of a theory or scientific belief. • A case study can be a source of new ideas that may be examined using other research methods. Achieve Page 9
Introduction to Psychology Disadvantages: • The major limitation of a case study is that it is a poor method for determining cause-effect relationships because, in most studies, explanations of behaviors occur after the fact and there is little opportunity to rule out alternative explanations. • A second problem concerns the generalizability of the findings, meaning, will the principles uncovered in a case study hold true for other people or in other situations. • A third problem is the possible lack of objectivity in the way data are gathered and interpreted, because case studies are often based on the researcher’s subjective impressions. Naturalistic Observation The researcher observes behavior as it occurs in a natural setting, and attempts to avoid influencing that behavior. Naturalistic observation is used to study human behavior. Naturalistic observation can yield rich descriptions of behavior in real-life settings and permits examination of relations between variables. Like case studies, naturalistic observation does not permit clear causal conclusions. In the real world, many variables simultaneously influence behavior, and they cannot be disentangled with this type of research technique. There is also the possibility of bias in how researchers interpret what they observe. Finally, the presence of an observer may disrupt a person’s or animal’s behavior. Correlational Research This type of research involves assessing the relationship between two variables. Because neither variable is manipulated, there is no way to determine if changes in one variable cause changes in the other. Only how changes in one are related to changes in the other can be determined. A positive relationship means that high scores in one variable tend to be paired with high scores in the other variable. A negative relationship means that high scores in one variable tend to be paired with low scores in the other variable. In addition to the direction of the relationship, a correlation coefficient will describe the strength of the relationship. The benefits of conducting correlational research include: establishing if relations found in the laboratory generalize to the outside world, and discovering associations that are subsequently studied under controlled laboratory conditions. Moreover, for practical or ethical reasons, some questions cannot be studied with experiments but can be examined in a correlational study, and correlation data allows us to make predictions.
Introduction to Psychology
© 2015 of 97 Survey Research Information about a topic is obtained by administering questionnaires to or conducting interviews with many people. In survey research, a population consists of all the individuals who are the target of the study. Because it is often impractical to study an entire population, a survey is administered to a sample group, which is a subset of individuals drawn from a larger population. To draw valid conclusions about a population from a survey, the sample must be representative. A representative sample is one that reflects the important characteristics of a population. When a representative sample is surveyed, the researcher can be confident that the findings closely portray those of the population as a whole. This is the strongest advantage of survey research. In scientific research, surveys are an efficient method for collecting a large amount of information about people’s opinions, experiences, and lifestyles, and they can reveal changes in people’s beliefs and habits over many years. Some of the drawbacks to survey research are that: survey data cannot be used to draw conclusions about cause and effect surveys rely on participants self-reports, which can be distorted by bias and under-representative samples can lead to faulty generalizations about how an entire population would respond. Experiment In experiments, researchers assess cause and effect relationships between at least two variables. The cause is represented by the independent variable and will always involve treating subjects in at least two different ways. Subjects in the experimental group are exposed to whatever the presumed “cause” is those in the control group are not exposed to the “cause.” The “effect” is represented by the dependent variable and will typically involve measuring how subjects behave. Because subjects are assigned randomly to each experimental condition, and because there is only one difference in how the experiment and control groups are treated, any difference in the behavior of those two groups must be due to that treatment (i.e., the independent variable). An experiment has three essential characteristics: • The researcher manipulates one or more variables. The independent variable refers to the factor that is manipulated or controlled by the experimenter. • The researcher measures whether this manipulation influences other variables. The dependent variable is the factor that is measured by the experimenter and may be influenced by the independent variable. • The researcher attempts to control extraneous factors that might influence the outcome of the experiment. Achieve Page 11
Introduction to Psychology The independent variable is viewed as the cause and the dependent variable as the effect. It is possible that subjects in an experimental group could behave differently than they normally would, because they know they are being exposed to special treatment. This is called the placebo effect. In order to determine the extent to which this might be happening, the control group subjects are sometimes told that they too are receiving a special treatment or drug, even when they are not. This fake special treatment or drug is called a placebo. If subjects don’t know whether or not they are receiving the placebo, the experiment is called a blind study. It is possible that experimenters can unwittingly influence results by knowing which subjects are receiving which treatment. Therefore, in a double-blind study, even the experimenters do not know if they are delivering the placebo or the drug. Although the experimental approach is a powerful tool for examining causality, researchers must avoid errors that can lead to faulty conclusions. Tests Psychologists develop and use specialized tests to measure many types of variables. For example, personality tests, which assess personality traits, often contain questions that ask how a person typically feels or behaves. Other psychological tests consist of performance tasks. For example, intelligence tests may ask people to assemble objects or solve arithmetic problems. Neuropsychological tests help diagnose normal and abnormal brain functioning by measuring how people perform mental and physical tasks, such as recalling lists of words or manipulating objects. To enhance learning and chances of performing well on tests, one can apply scientific psychological principles regarding time management, strategies for studying more effectively, test preparation strategies, and techniques for taking tests. Statistical Methods Statistics are woven into the fabric of modern life, and they are integral to psychological research. Typically, it is difficult to make sense out of the data collected by examining the individual score of each participant. Descriptive statistics allow us to summarize and describe the characteristics of a set or distribution of data. Descriptive- Two types of descriptive statistics are measures of central tendency and measures of variability. Measures of Central Tendency - Given a set of data, measures of central tendency address the question “What is the typical score?” One measure, the mode, is the most frequently occurring score in a distribution. A second measure is the median, the point that divides a distribution of scores in half when those scores are arranged in order from lowest to highest. Finally, the mean is the arithmetic average of a set of scores. Because the mean takes all the information in a set of scores into account, it is the most commonly used measure of central tendency.
Introduction to Psychology Measures of Variability - To describe a set of data, researchers want to know, not only the typical score, but also whether the scores cluster together or vary widely. Measures of variability capture the degree of variation or spread in a distribution of scores. The simplest but least informative measurement is the range, which is the difference between the highest and lowest scores in a distribution. A more important statistic is the standard deviation which takes into account howmuch each score in a distribution differs from the mean. Inferential- Descriptive statistics allow researchers to efficiently summarize data, but researchers typically want to go beyond mere description and draw inferences (conclusions) from their data. Inferential statistics tell us how confident one can be in making inferences about a population, based on findings obtained from a sample. • Null Hypothesis- A null hypothesis is a hypothesis that proposes no relationship or difference between two variables. • Alternative Hypothesis- Proposes a relationship between two or more variables. • Statistical Significance- Means that it is very unlikely that a particular finding occurred by chance alone. Psychologists typically consider results to be statistically significant only if the results could have occurred by chance alone in fewer than 5 times in 100. 1.4 Psychological Specialties Psychology is the scientific study of behavior and the mind. The term ‘behavior’ refers to actions and responses that we can directly observe, whereas the term ‘mind’ refers to internal states and processes, such as thoughts and feelings that cannot be seen directly and that must be inferred from observable, measurable responses. Because psychologists’ study biological, psychological, and environmental factors that affect a wide array of behaviors, psychological science intersects with many other disciplines and many subfields and areas of specialty have developed. • Clinical Psychology- The study and treatment of mental disorders. Many clinical psychologists diagnose and treat people with psychological problems in clinics, hospitals, and private practice. Some are also scientists who conduct research on the causes of mental disorders and the effectiveness of various treatments. • Biopsychology- Focuses on the biological underpinnings of behavior, examining how the brain processes, genes, and hormones influence our actions, thoughts, and feelings. • Developmental Psychology- Examines human physical, psychological, and social development across the life span. • Experimental Psychology- Focuses on basic processes such as learning, sensory systems, perception, and motivational states. Most research in this field involves laboratory experiments, often with nonhuman animals. • Industrial-organizational Psychology- Examines people’s behavior in the workplace. • Psychometrician- Practices the science of measurement, or psychometrics. The term psychometrics refers to the measurement of an individual's psychological attributes,
Introduction to Psychology including the knowledge, skills, and abilities a professional might need to work in a particular job or profession. • Personality Psychology- Focuses on the study of human personality. • Social Psychology- Examines people’s thoughts, feelings, and behavior pertaining to the social world. Studies how people influence each other, behave in groups, and form impressions and attitudes. Science involves both basic research, which reflects the quest for knowledge for its own sake, and applied research, which is designed to solve specific, practical problems. For psychologists, most basic research examines how and why people behave, think, and feel the way they do. In applied research, psychologists often use basic scientific knowledge to design interventions. Modern psychologists work in many settings. They teach, conduct research, perform therapy and counseling, and apply psychological principles to enhance human welfare and help shape public policy.
Introduction to Psychology
Chapter 1 Practice Quiz 1. Which branch of psychology seeks to examine behaviors and thoughts pertaining to the workplace? a. Social Psychology b. Clinical Psychology c. Industrial-Organizational Psychology d. Developmental Psychology 2. True or False: Inferential statistics describes a set of data including measures of central tendency. a. True b. False 3. Marcy wishes to ask all of the students in a high school about their drinking habits. Which method of research should she pursue in order to get effective and efficient data? a. Survey b. Naturalistic Observation c. Experiment d. Case Study 4. Which hypothesis states that there is no relationship between the independent and dependent variable? a. Alternative Hypothesis b. Null Hypothesis
5. Which perspective of psychology emphasizes free will and personal growth? a. Evolutionary Psychology b. Social Psychology c. Developmental Psychology d. Humanistic Psychology 6. B.F. Skinner was one of the leading pioneers in research for: a. Behaviorism b. Classical Conditioning c. Psychodynamic Training d. Gestalt psychology 7. True or False: An animal behaviorist may use naturalistic observation to record data about a species in their undisturbed habitat. a. True b. False 8. All of the following research methods are feasible for studying large groups EXCEPT: a. Survey b. Experiment c. Case Study d. Longitudinal Study
Introduction to Psychology
Chapter Two: Biological Influences n Behavior Learning Objectives After completing Unit Two, you will be able to: 1. Describe the biological bases of behavior, by discussing the impact of genetic influences on behavior 2. Describe the impact of evolution on behavior, utilizing five evolution theories and their impact on behavior 3. Discuss environmental influences on behavior 4. Describe the influence of hormones on behavior 5. Describe the hierarchical brain structures and behavioral functions 2.1 Genes, Evolution, and Environment Humans have wondered how physical characteristics are transmitted from parents to their offspring. Many have wondered how genetics influence behavior and how people adapt to their environment. Genetic Influences Early in the 20th century, geneticists made the important distinction between genotype (the specific genetic makeup of the individual), and phenotype (the individual’s observable characteristics). Genes and Heritability 1. Individual Differences- At a biological level, genes direct the process of development by programming the formation of proteinmolecules, which can vary in infinite ways. Heredity potential is carried in the genes and genotype is present from conception. 2. Group Differences- Phenotype can be affected by both genes and the environment. Genetic structure and phenotype are not identical, in part because some genes are dominate while others are recessive and many characteristics are influenced by the interactions of multiple genes.
Introduction to Psychology of 97 The egg cell from the mother and the sperm cell from the father carry within their nuclei the material of heredity, in the form of rod like units called chromosomes. A chromosome is a double stranded and tightly coiled molecule of DNA. All of the information for heredity is encoded in the combinations of four chemical bases - adenine, thymine, guanine, and cytosine - that occur throughout the chromosome. Within each DNA molecule, the sequence of the four letters of the DNA alphabet - A, T, G, C - creates the specific commands for every feature and function of the person. The DNA portion of the chromosome body carries the genes, the biological units of heredity. With the exception of the egg and sperm cells, every cell in the body carries within its nucleus 23 pairs of chromosomes, each containing numerous genes that regulate every aspect of cellular functioning. Every cell nucleus in the body contains the genetic code for the entire body. Genome In 1990, geneticists began the Human Genome Project, a coordinated effort to map DNA, including all the genes, of the human organism. The genetic structure in every one of the 23 chromosome pairs has now been mapped, by methods that allow investigators to literally disassemble the genes in each chromosome and study their specific sequences of bases (A,T,G, and C). The first results of the genome project showed that the human genome consists of approximately 25,000 genes and the location and structure of more than 80 genes that contribute to hereditary diseases have been identified through gene mapping. Evolution The separate paths of behaviorism and ethology have increasingly converged, reminding us that the environment shapes behavior in two fundamental ways: through species adaptation and through personal adaptation. Our personal adaptation to life’s circumstances occurs through the laws of learning, resulting from our interactions with immediate and past environments. The environment also influences species adaptation. Over the course of evolution, the environmental conditions faced by each species helped shape biology. Theorists proposed that, as the human brain evolved, it acquired capacities that enhanced our ability to learn and solve problems. Evolution is a change over time in the frequency with which particular genes, and the characteristics they produce, occur within an interbreeding population. • Charles Darwin- He was an English naturalist and geologist, best known for his contributions to evolutionary theory. He established that all species of life descended over time from common ancestors. He introduced the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect as the artificial selection involved in selective breeding. © 2015 Achieve Page 17
Introduction to Psychology • Natural Selection- Characteristics that increase the likelihood of survival and reproduction within a particular environment are more likely to be preserved in the population, and therefore become more common in the species over time. As environmental changes produce new and different demands, various new characteristics may contribute to survival and the ability to pass on one’s genes. In this way, natural selection acts as a set of filters, allowing certain characteristics of survivors to become more common. • Instincts/Mental Modules- Darwin’s theory of evolution inspired many early psychological views that instincts motivate much of our behavior. An instinct is an inherited characteristic, common to all members of a species that automatically produces a particular response when the organism is exposed to a particular stimulus. To evolutionary psychologists, what we call human nature is the expression of inborn biological tendencies that have evolved through natural selection. • Universal Traits- Culture plays an important role in shaping our present and past experiences, and strongly affects howwe learn. Cultural socialization influences our beliefs and perceptions, our social behavior, our sense of identity, the skills we acquire, and countless other characteristics. Learning is the mechanism through which the environment exerts its most profound effects on behavior. • Courtship and Mating- The only way to continue the species is through reproduction. In order to pass on one’s genes and maintain the species, people must mate. One of the most important and intimate ways that humans relate to one another is by seeking a mate. Marriage seems to be universal across the globe. In seeking mates, women and men display different mating strategies and preferences. According to an evolutionary viewpoint, called sexual strategies theory, mating strategies and preferences reflect inherited tendencies, shaped over the ages in response to the different types of adaptive problems that men and women faced. Another theory, referred to as the social structure theory, maintains that men and women display different mating preferences, not because nature impels them to do so, but because society guides them into different social roles. 2.2 Environmental Influences Nature vs. Nurture Behavior geneticists study how genetic and environmental factors contribute to the development of psychological traits and behaviors. Adoption and twin studies are the major research methods used to disentangle hereditary and environmental factors. The environment exerts its effects largely through learning processes, made possible by innate biological mechanisms. Humans and other
Introduction to Psychology animals can learn which stimuli are important and which responses are likely to result in goal attainment, thereby allowing them to regulate their behavior and adapt to the environment. • Personality- Personality has a strong genetic contribution, though not as strong as that for intelligence. Shared family environment seems to have little impact on the development of personality traits. Unshared individual experiences are far more important environmental determinates. • Intelligence- Intelligence has a strong genetic basis, with the individual inheriting a range for potential intelligence that has upper and lower limits measured through IQ testing. Environmental effects will then determine where the person falls within these genetically determined boundaries. 2.3 Nervous System The evolutionary history of our species, the genes inherited from parents, and life experiences have shaped us. From a psychological perspective, the most important physical organ is the brain. To understand how the brain controls experience and behavior, we must first understand how its individual cells function, and how they communicate with one another. Neurons- Neurons are the basic building blocks of the nervous system and are the pathways for communication. They are also referred to as nerve cells. Components of the Neuron- Each neuron has three main parts: a cell body, dendrites, and an axon. The cell body, or soma, contains the biochemical structures needed to keep the neuron alive, and its nucleus carries the genetic information that determines how the cell develops and functions. Emerging from the cell are branch-like fibers, called dendrites, which are specialized receiving units like antennae that collect messages from neighboring neurons and send them on to the cell body. There, the incoming information is combined and processed. All parts of a neuron are covered by a protective membrane that controls the exchange of chemical substances between the inside and outside of the cell. These exchanges play a critical role in the electrical activities of nerve cells. Extending from one side of the cell body is a single axon, which conducts electrical impulses away from the cell body to other neurons, muscles, or glands. Many axons that transmit information throughout the brain and spinal cord are covered by a tube-like myelin sheath, a whitish fatty insulation layer which accelerates the transmission of information. Synapse- The parts of a single neuron are physically connected, so electrical signals are able to travel from one end of the neuron to the other without interruptions. Between neurons, however, is a small gap. The junctions where the end of one neuron meets the beginning of another is called a synapse and the gap between them is called the synaptic gap. Communication across this gap is accomplished with neurotransmitters, rather than with electrical impulses. Nerve Impulse- Neurons do their work through the use of electrical impulses and neurotransmitters. A signal (information) from a sense receptor or another neuron, coming in through a neuron’s
Introduction to Psychology of 97 dendrites, gets passed along when it triggers an action potential, or electrical impulse, that travels down the axon and then triggers activity in whichever neurons, muscles, or glands join up with the axon. Neurons do two important things. Like tiny batteries, they generate electricity that creates nerve impulses. They also release chemicals that allow them to communicate with other neurons and muscles and glands. At rest, the neuron has an electrical resting potential due to the distribution of positively and negatively charged chemical ions inside and outside of the neuron. When stimulated, a flow of ions in and out through the cell membrane reverses the electrical charge of the resting potential, producing an action potential, or nerve impulse. The original ionic balance is restored, and the neuron is again at rest. Neurotransmitters- Are chemical molecules contained in vesicles, or sacs, within the axon terminal. When an action potential, or electrical impulse arrives at the terminal, the neurotransmitters are released into the synaptic cleft. They then bind to receptor sites on the next neuron’s dendrites. The neurotransmitters are chemical substances that carry messages across the synaptic space to the other neurons, muscles, or glands. Different neurotransmitters affect different neurons. Because different neural pathways are made up of different neurons and have different functions, each neurotransmitter affects behavior differently. Endorphins- Most neurotransmitters have their excitatory and inhibitory effects only on specific neurons that have receptors for them. Others, called neuromodulators, have a more widespread and generalized influence on synaptic transmission. These substances circulate through the brain and either increase or decrease the sensitivity of neurons to their specific transmitters. The best-known neuromodulators are the endorphins, which travel through the brain’s circulatory system and inhibit pain transmission, while enhancing neural activity that produces pleasurable feelings. Central Nervous System- The central nervous system includes the brain, which controls many physiological and psychological functions, and the spinal cord, which enables reflexive behavior and relays information to the brain from elsewhere in the body. Brain- Neuroscientists use four different methods to study the brain’s structures and activities, through various research methods. Research Methods- Because of scientific and technical advances, more has been learned about the brain in the past four decades than was known throughout the preceding ages. Neuropsychological Tests- Psychologists have developed a variety of neuropsychological tests to measure verbal and nonverbal behaviors of people who have suffered brain damage through accident or disease. The Trial Making Test is used to assess brain function, testing memory and planning. Scores on the test give an indication of the type and severity of brain damage. The tests are also used to assess learning disabilities and developmental disorders. Destruction and Stimulation Techniques- Experimental studies are another useful method of learning about the brain. In this method, researchers chemically or electrically stimulate the neurons. In chemical stimulations, a tiny tube, or cannula, is inserted into a precise area of the brain so that © 2015 Achieve Page 20
The excitatory neurotransmitter glutamate is released from hippocampal formation principal cells and is therefore the neurotransmitter utilized by the perforant path, mossy fibers, and Schaffer collaterals. Glutamate receptor subtypes include the ionotropic receptors (iGluRs) that are ligand-gated cation channels and are named after the ligands that preferentially bind to them: N-methyl- d -aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and kainate. All of the iGluRs are present in the excitatory pathways of the hippocampus. AMPA and kainate receptors mediate fast excitatory postsynaptic potentials (EPSPs), and NMDA receptors mediate slower EPSPs. All of the iGluRs are permeable to Na + NMDA as well as some AMPA and kainate receptors are also permeable to Ca 2+ . The NMDA receptor is unique in that channel permeability is both ligand and voltage dependent.
There is also a family of metabotropic glutamate receptors (mGluRs) that are coupled to guanine nucleotide-binding proteins (G-proteins). mGluRs have both pre- and postsynaptic localization and can coexist in the postsynaptic density with iGluRs. When expressed presynaptically, mGluR activation can modulate transmitter release. Postsynaptically, mGluRs regulate synaptic transmission by stimulating specific second messenger cascades and generating slow synaptic responses, and may mediate long-term depression in the hippocampus. 26
The inhibitory neurotransmitter GABA can also act on both ionotropic and metabotropic receptors. GABAA receptors are ligand-gated ion channels that are permeable to the anion Cl − . GABA also binds a metabotropic receptor, GABAB, which is coupled to a G-protein that when activated opens K + channels. When expressed postsynaptically, GABAB receptor activation leads to a slow hyperpolarization. When expressed presynaptically, GABAB receptor activation reduces neurotransmitter release.
Balancing the neurotransmitters
How do we even know if our neurotransmitters are out of balance? Symptoms of mood disorders, sleep disorders, or cloudy thinking are often the reasons that people seek help from a physician for prescriptions to help increase neurotransmitters. Many drugs that treat illnesses like depression are basically synthetic neurotransmitters.
Other drugs work to by block the receptors of neurons so that the neurotransmitter’s message is not received. Blocking a neurotransmitter is helpful to balance the brain’s chemicals when there is too much of one of the neurotransmitters. Here are some ways that you can balance the neurotransmitters in your brain.
How does neurotransmitter distribution and usage vary thought the brain? - Psychology
Other, less common kinds of synapses include axoaxonic synapses (involved in presynaptic inhibition phenomena) and dendrodendritic synapses.
However, a nerve impulse can also be transmitted from a sensory receptor cell to a neuron, or from a neuron to a set of muscles to make them contract, or from a neuron to an endocrine gland to make it secrete a hormone. In these last two cases, the connection points are called neuromuscular and neuroglandular junctions.
In a typical chemical synapse between two neurons, the neuron from which the nerve impulse arrives is called the presynaptic neuron. The neuron to which the neurotransmitters (chemical messengers) bind is called the postsynaptic neuron.
A presynaptic neuron has several specialized structures that distinguish it from a postsynaptic neuron.
The terminal button of the presynaptic neuron&rsquos axon contains mitochondria as well as microtubules that transport the neurotransmitters from the cell body (where they are produced) to the tip of the axon.
(click on 2. Axonal Transport)
This terminal button also contains spherical vesicles filled with neurotransmitters . These neurotransmitters are secreted into the synaptic gap by a process called exocytosis, in which the vesicles&rsquo membranes fuse with that of the presynaptic button.
The synaptic gap that the neurotransmitters have to cross is very narrow&ndashon the order of 0.02 micron.
Across the gap, the neurotransmitters bind to membrane receptors: large proteins anchored in the cell membrane of the post-synaptic neuron. At this location, under an electron microscope, you can observe an accumulation of opaque material which consists of the cluster of receptors and other signalling proteins that are essential for chemical neurotransmission.
Any given neurotransmitter has several sub-types of receptors that are specific to it. It is the presence or absence of certain of these sub-types that causes a cascade of specific chemical reactions in the postsynaptic neuron. These reactions result in the excitation or inhibition of this neuron.
An antagonist is a molecule that blocks the effect that the neurotransmitter normally has on the post-synaptic neuron.
|It was long thought that a given neuron released only one kind of neurotransmitter. But today, many experiments show that a single neuron can produce several different neurotransmitters.|
|Neurons that use GABA and glutamate as neurotransmitters are used by more than 80% of the neurons in the brain and constitute the most important inhibition and excitation systems, respectively, of the substantia nigra pars compacta (SNc).|
This section describes a few of the best known neurotransmitters that are involved in many functions in both the central and the peripheral nervous systems. Apart from acetylcholine, they all belong to the family of amines or amino acids.
Types of Neurotransmitter
The type of neurotransmitter depends on the type of synapses utilized.
The synaptic cleft, presynaptic terminal, and receiving dendrite of the next cell together form a junction known as the synapse (2).
There are different types of synapses but
they all transmit messages of two types.
These types vary in appearance and location
Type I synapses:
- Location: Dendrite spine or shafts
- Characteristic feature: round synaptic vesicles
- Examples: Neurotransmitters that use these synapses are Acetylcholine Epinephrine,Glutamate, Histamine, dopamine
Type II synapses
- Location: cell body.
- Characteristic feature: flattened vesicles
- Examples: Some Neurotransmitters that use these synapses are Serotonin, GABA, Glycine.
The neurotransmitter release mechanisms are
impaired in many diseases like Schizophrenia, Depression, Alzheimer's disease