Psychology involves the study of
The behavior of other people, one’s own behavior, and how our behavior is affected by groups and social influences
-psychologists are interested in studying behavior in nonhuman species as well
-studies of behavior of other animals
can shed light on basic principles of behavior and may help inform our understanding of our own behavior as well
The science of behavior and mental processes
-psychology is derived from two Greek roots: psyche, meaning mind, and logos, meaning “study” or “knowledge”
Anything an organism does
Private experiences that constitute our inner lives- include thoughts and feelings, dreams and daydreams, sensations, perceptions, and beliefs that others cannot directly observe or experience
Psychology is a science because
It applies the scientific model in testing claims and beliefs in the light of evidence
-credited the
founding of psychology as an experimental science
-in 1879 in the city of Leipzig Germany, he established the worlds first scientific laboratory dedicated to the study of psychology
-as a boy Wundt was a poor student because he tended to daydream in class
-he eventually graduated from medical school and launched a successful research career as a physiologist
-Wilhelm Wundt was interested in studying mental experiences. He used a
method called introspection, which is an attempt to directly study consciousness by having people report on what they are consciously experiencing
-Wundt and his students sought to break down mental experiences into their component parts, including sensations, perceptions, and feelings, and then discover the rules that determine how these elements come together to produce the full range of conscious experiences
-brought wundt’s teachings and methods of introspection to the United States and other English speaking countries
School of psychology identified with Wundt and titchener
An approach that attempted to define the structure of the mind by breaking down mental experiences into their component parts
-first American to work in wundt’s experimental laboratory
-in 1892 Hall founded the American psychological
association (APA), now the largest organization of psychologists in the United States, and he served as its first president
-nine years earlier he had established the first psychology laboratory in the United States, which was housed at Johns Hopkins university
William James and functionalism
-William James was trained as a medical doctor but
made important contributions to both psychology and philosophy
-James founded functionalism, the school of psychology that focused on how behavior helps individuals adapt to demands placed upon them in the environment
-whereas structuralists were concerned with understanding the structure of the human mind, functionalists were concerned with the functions of mental processes
-James did not believe that conscious experience can be parceled into discrete elements
-functionalist
examined the roles or functions of mental processes- why we do what we do
John Watson and behaviorism
-in the early 1900s, a new force in psychology gathered momentum called behaviorism- its credo was that psychology should limit itself to the study of overt behavior that observers could record and measure
-founder of behaviorism was
American psychologist John Watson
-Watson reasoned that because you can never observe another person’s mental processes, psychology would never advance as a science unless it eliminated mentalistic concepts like mind, consciousness, thinking and feeling
-he rejected introspection as a method of scientific inquiry and proposed that psychology should become a science of behavior, not of mental processes
-Watson believed that the environment molds the behavior of humans and other
animals
- behaviorism became the main school of psychology in the United States by the 1920s, and remained the dominant force in American psychology for several generations
Problem with introspection
There is no way to directly observe a person’s mental experiences or know how one person’s feelings or sensations compare to another’s
-skinner studied how behavior is shaped by rewards and punishments, the environmental consequences that follow specific responses
-skinner showed he could train animals to perform simple behaviors by rewarding particular responses
-skinner also showed how complex behaviors could be learned and maintained by manipulation of rewards, which he called reinforcers
-skinner believed the same principles of learning he observed in lab
animals could be applied to humans as well
-he argued that human behavior is as much a product of environmental consequences as the behavior of other animals
Max Wertheimer and Gestalt Psychology
-gestalt psychology: the school of psychology that studies ways in which the brain organizes and structures our perceptions of the world
-wertheimer
noticed on a train one day that objects in the distance appeared to be moving along with the train, even though they were obviously standing still. He believed the illusion was not a truck of the eye but reflected higher level processes in the brain that created a false perception of movement
The gestalt psychologists rejected the structuralist belief that mental experience could be understood by breaking it down into its component
parts
-German word gestalt can be roughly translated as “unitary form” or “pattern”.
-gestalt psychologists believe the brain organizes our perceptions of the world by grouping elements together into unified or organized wholes, rather than as individual bits and pieces of sense experience
-“the whole is greater than the sum of the parts”
Sigmund Freud and psychoanalysis
-Freud’s psychology focused not only on the mind, but also on a region of the mind that lay beyond the reach of ordinary consciousness- a region he called the unconscious
-Freud conceived of the unconscious as the repository of primitive sexual and aggressive drives or instincts and of the wishes, impulses, and urges that arise from those drives or instincts.
-believed that the motives underlying our behavior involves sexual and aggressive
impulses that lie in the murky depths of the unconscious, hidden away from our ordinary awareness of ourselves.
-Freud also believed that early childhood experiences play a determining role in shaping our personalities and behavior, including abnormal behaviors like excessive fears or phobias. He held that abnormal behavior patterns are rooted in unconscious conflicts originating in childhood
Psychodynamic perspective
Freud’s view of psychology
Freud’s main aim was to help people overcome psychological problems
-he developed a form of psychotherapy or talk therapy that he called psychoanalysis
-psychoanalysis incorporates methods, such as analysis of dreams and slips of the tongue, that Freud believed could be used to gain insight into the nature of the underlying
motivates and conflicts of which his patients were unaware
-Freud maintained that once these unconscious conflicts were brought into the light of conscious awareness they could be successfully resolved during the course of therapy
Six major perspectives of psychology
Behavioral, psychodynamic, humanistic, physiological, cognitive, and sociocultural
-Behaviorism: the belief that environmental influences determine behavior and that psychology should restrict itself to the study of observance behavior
-traditional behaviorism is no longer the dominant force it was during the 1900s
-new perspective called social cognitive theory: belief that behavior is shaped not only by environmental factors, but also by cognitive factors such as the value placed on different
objects or goals and expectancies about the outcomes of behavior
-social cognitive theorists challenged their fellow psychologists to find ways to study these mental processes rather than casting them aside as unscientific, as traditional behaviorists would
Behavior therapy involves the systematic application of learning principles that are grounded in the behaviorist tradition of Watson and skinner
- behavior therapists help people
acquire more adaptive behaviors to overcome psychological problems such as fears and social inhibitions
-today, many behavior therapists subscribe to a broader therapeutic approach, called cognitive behavioral therapy, which incorporates techniques for changing maladaptive thoughts as well as overt behaviors
Psychodynamic perspective
-continues to
evolve
-“neo-freudians” tend to place less emphasis on basic drives like sex and aggression than Freud did and more emphasis on processes of self awareness, self direction, and conscious choice
-humanistic psychologists rejected the deterministic views of behaviorism and psychodynamic psychology- beliefs that human behavior is determined by the environment or by the interplay or unconscious forces and motives lying outside the
person’s awareness- and instead believe that free will and conscious choice are essential aspects of the human experience
-psychologists who adopt the humanistic perspective believe that psychology should focus on conscious experiences, even if those experiences are subjective and cannot be directly observed and scientifically measured
-humanistic psychologists view each of us as individuals who possess distinctive clusters of traits and abilities and unique frames of reference or
perspectives on life. They emphasize the value of self awareness and of becoming an authentic person by being true to oneself. They also stress the creative potentials of individuals and their ability to make choices that imbue their lives with meaning and purpose
Physiological perspective
-the physiological perspective examines relationships between
biological processes and behavior
-it is identified not with any one contributor but rather with many psychologists and neuroscientists who focus on the biological bases of behavior and mental processes
-a movement within modern psychology that applies principles derived from Charles Darwin’s theory of evolution to a wide range of behavior
-Darwin believed that all life forms evolved from earlier life forms by adapting over time
to the demands of their natural environments
-evolutionary psychologists believe that behavioral tendencies or predispositions might be rooted in our genes, having been passed along from generation to generation from ancestral times all the way down the genetic highway to us
-evolutionary psychologists examine behaviors in different species that may have been influenced by evolutionary processes, including aggression, mating practices, and even altruism while recognizing that
environmental factors such as cultural learning and family influences play important roles in determining whether behavioral tendencies or predispositions lead to actual behavior
-psychologists working from a cognitive perspective study mental processes, including thinking, learning, memory, use of language, and problem solving
-these processes enable people to gain knowledge about themselves and the world around them
-cognitive
psychologists believe the methods they use to study thinking or cognition are well grounded in the scientific tradition.
Sociocultural perspective
-psychologists who adopt a sociocultural perspective examine how behavior and attitudes are shaped by social and cultural influences to which people are exposed
-they focus on the influence of such
factors as age, ethnicity, gender, sexual orientation, lifestyle, income level, disability status, and exposure to discrimination and prejudice
-study of sociocultural factors in shaping behavior is especially relevant today because of the increasing diversity of American society
-sociocultural perspective poses a number of questions: does susceptibility to visual illusions vary across culture? Are there gender differences in basic abilities in math or verbal skills? How does culture
influence concepts of the self?
-psychologists recognize that research samples need to be broadly representative of the populations to which they wish to generalize their findings
-directed toward the study of positive aspects of human experience, such as love, happiness, altruism, and hope
-psychologists have devoted a great deal of attention to understanding human weaknesses and deficits, including emotional problems, effects
of traumatic stress, and problem behaviors such as violence and drug addiction
-positive psychology balanced the scale by focusing on our virtues and strengths, not our flaws
______ is the earliest school of psychology
Structuralism
-it was identified with Wilhelm Wundt and Edward titchener, and it attempted to break down mental experiences
into their component parts- sensations, perceptions, and feelings
______ is the school of psychology founded by William James
Functionalism
-it attempts to explain our behavior in terms of the functions it serves in helping us adapt to the environment
_____ is the school of psychology begun by James Watson
Behaviorism
-it holds that psychology should limit itself to observable phenomena- behavior
_____ psychology is the school of psychology founded by Max Wertheimer
Gestalt
-it is grounded in the belief that
the brain structures our perceptions of the world in terms of organized patterns or wholes
______, the school of thought originated by sigmund Freud, emphasizes the role of unconscious motives and conflicts in determining human behavior
The ______ perspective focuses on observable behavior, the role of learning, and the importance of environmental influences on behavior
The _______ perspective represents the model of psychology developed by Freud and his followers. It holds that our behavior and personalities are shaped by unconscious motivates and conflicts that lie outside the range of ordinary awareness
The ______ perspective reflects the views of humanistic psychologists such as Carl Rogers and Abraham Maslow, who emphasized the importance of subjective conscious experience and personal freedom and responsibility
The _____ perspective examines the ways in which behavior and mental experience are influenced by biological processes such as heredity, hormones, and the workings of the brain and other parts of the nervous system
The _____ perspective focuses on mental processes that allow us to gain knowledge about ourselves and the world
The ______ perspective examines how our behavior and attributes are shaped by social and cultural influences
William James is to functionalism as ______ is to structuralism
The early school of psychology called structuralism investigated
The structure of the mind
Which of the early schools of psychology believed that psychology should be limited to the study of observable behavior
Gestalt psychology focuses on
The ways in which the brain organizes and structures our perceptions of the world
Humanistic psychologists rejected the notion that unconscious processes and environmental influences determine our behavior. Rather, they emphasized the importance of _____ in understanding behavior
Which psychological perspective originated with sigmund Freud?
Psychodynamic perspective
Study relationships between the brain and behavior. Although some neuropsychologists limit their activities to research, clinical neuropsychologists use specialized tests to evaluate the cognitive effects of brain injuries and strokes. These tests can help then pinpoint the particular areas of the brain affected by injury or disease. Clinical neuropsychologists may also work with rehab specialists in designing programs to help people who have suffered various forms of brain damage regain as much of their functioning as possible.
Focus on psychological processes associated with aging. They may work with geriatric patients to help them cope with the stresses of later life, including retirement, loss of loved ones, and declining physical health
Work within the legal system. They may perform psychological evaluations in child custody cases, testify about the competence of defendants to stand trial, develop psychological profiles of criminal types, give expert testimony in court on psychological issues, or assist attorneys in selecting potential jury members
Apply psychological principles and techniques to sports and athletic competition. They help athletes develop relaxation skills, and use positive self talk and mental focusing skills to overcome performance anxiety and enhance athletic performance. They also study why athletes sometimes choke in critical game situations
-completed all doctoral degree requirements at Johns Hopkins university but was not awarded the doctoral degree because the university did not issue doctoral degrees to women at that time
Completed all her PhD requirements at Harvard but Harvard denied her a doctorate- it did not grant doctoral degrees to women.
Describe ethnic and gender characteristics of psychologists today and the changes that have occurred over time
Though psychology is now a more diverse discipline, African Americans and other minority groups remain underrepresented in the professional ranks of psychologists. Unlike the early days of the profession, when women were actively excluded from pursuing professional careers, they now constitute more than two thirds of new phds in psychology
___ research focuses on expanding our understanding and knowledge, whereas ____ research focuses on finding answers or solutions to particular problems
Help students adjust to college life
Developmental psychologists
Study changes in behaviors and attitudes throughout the life cycle
Environmental psychologists
Study effects of outdoor temperature on aggression
Study psychological characteristics of people who buy particular products
First African American to receive a doctorate in psychology in the United States
Like other scientific disciplines, psychology uses the ________ in its pursuit of knowledge
Framework for acquiring knowledge based on careful observation and the use of experimental
methods. It can be conceptualized in terms of four general steps that scientists use to test their ideas and to expand and refine their knowledge:
1. Developing a research method
2. Framing the research question in the form of a hypothesis
3. Gathering evidence to test the hypothesis
4. Drawing conclusions about the hypothesis
Developing a research question
Psychologists generate research questions from many sources, including theory, careful observation, previous experience, and commonly held beliefs
Framing the research question in the form of a hypothesis
An investigator reframes the research question In the form of a hypothesis- a precise prediction that can be tested through research. Hypotheses are often drawn from theory. Based on a theoretical model, an investigator might frame the research question in the form of a testable hypothesis.
Investigators may also develop hypotheses based on common beliefs or assumptions about behavior.
Gathering evidence to test the hypothesis
The investigator develops a research design or strategy for gathering evidence to provide a scientific test of the hypothesis. The type of research method used depends on the nature of the problem.
Drawing conclusions about the hypothesis
Investigators draw conclusions about their hypotheses based on the evidence their research has produced. To
test their hypotheses, they turn to statistics- the branch of mathematics involving methods of tabulating and analyzing numerical data.
-investigators use statistical methods to determine whether relationships between variables or differences between groups are statistically significant.
-a variable is a factor that varies in an experiment
When research findings do not support the study’s hypothesis, scientists may
Adjust the theories from which the hypotheses were derived. Research findings may suggest new avenues of research or revision of the psychological theories themselves
Psychologists propose testable ________ that guide their research
-important factor in drawing conclusions
-the attempt to
duplicate findings reported by others to determine whether they will occur again under the same experimental conditions
-scientists have more confidence in findings that others can reliably replicate
5 methods scientists employ to acquire knowledge about behavior and mental processes
Case study, survey, naturalistic observation, correlational, and experimental methods
-the case study method is an in depth study of one or more individuals. The psychologist draws information from interviews, observation, or written records
-many of the early findings on brain function came from studies of brain injured patients that matched the types of injuries they sustained with particular deficits in memory functioning and motor skills
-problems with case studies can arise when
investigators rely on people’s memories of their past experiences, because memories can become distorted or filled with gaps
-people may also withhold important information out of embarrassment or shame- some people even purposefully deceive a researcher
-interviewers May heat only what they expect or want to see
-though case studies can provide a treasure trove of information and lead to testable hypotheses, they lack rigorous controls of scientific experiments
-gathers information from target groups of people through the use of structured interviews or questionnaires
-a structured interview is a questioning technique that follows a preset series of questions in a particular order
-questionnaire
-psychologists and other researchers conduct survey research to learn about the characteristics, beliefs, attitudes, and behaviors of certain populations
-in survey research, a population represents the
total group of people who are the subjects of interest. Because it would be impractical to study an entire population, surveys are conducted on samples, of segments of populations
-to draw conclusions about a population based on the results of a sample, the sample must be representative of the target population
A questioning technique that follows a preset series of questions in a particular order
A written set of questions or statements to which people can reply by marking responses in an answer form
Representative samples allow researchers to _______, or transfer, their results from a sample to the population it represents
To create representative samples, researchers use _________, a technique whereby individuals are selected at random from a given population for participation in a sample
Random sampling
-this often entails the use of a computer program that randomly selects names of individuals or households within a given population
-political polls reported in the media typically use random samples of voters to predict outcomes of elections
Like case studies, surveys may be limited by
Gaps in people’s memories
-participants may give answers that they believe are socially desirable rather than reflective of what they truly feel or believe
-ex) many people exaggerate how frequently they attend church
-social desirability may be especially strong in situations where people have a considerable stake in what others
think of them, such as on job interviews
This arises when people who volunteer to participate in surveys or other research studies are not representative of the population from which they are drawn
Naturalistic observation method
-takes the laboratory “into the field” to directly observe the
behavior of humans or other animal species in their natural habitats or environments
-the people or animal subjects serving as research participants may behave more naturally in their natural environments than they would in the artificial confines of the experimental laboratory
-because people may act differently when they know they are being observed, the observers try to avoid interfering with the behaviors they are observing
-to further minimize the potential bias, the observers
may spend time allowing the subjects to get accustomed to then so that they begin acting more naturally before any actual measurement takes place
-observers may also position themselves so that the subjects cannot see them
Psychologists have observed children at home with their parents to learn more about
Parent child interactions
Though the method of naturalistic observation may lack the controls available in controlled experiments, it can provide
Important insights into behavior as it occurs under natural conditions
Problems with naturalistic observation method
-problems with this method may arise if observers introduce their own biases
-if observers have a preconceived idea about how a parents interaction with a child affects the child’s behavior, they may tend to see what they expect to see
To guard against this, pairs of observers may be used to check for consistency between observers. Experimenters may also make random spot checks to see that observers are recording their measurements accurately
Animals in laboratory or zoo like environments may act differently than they do in their natural habitats. To learn more about chimp behavior, Jane Goodall lived for many years among chimpanzees in their natural environment. Her observations disputed the long held belief that only humans use tools
Psychologists use the correlational method to examine relationships between variables.
With the naturalistic observation method, researchers in the field can ______________, but they run the risk of _________.
Examine behavior as it unfolds; influencing the behavior they are observing
A statistical measure of association between two variables. Correlation coefficients can vary from +1.00 to -1.00. Coefficients with a positive sign represent a positive correlation in which higher values on one variable are associated with higher values on the other variable. Negative correlation, which is denoted by the negative sign, means the reverse: higher values on one variable are associated with lower values on the other.
Correlations are useful because
They allow us to predict one variable on the basis of the other. A perfect correlation of either +1 or -1 allows us to predict with certainty.
That there is no relationship between two variables; one variable is of no value in predicting the other
Two variables being correlated does not indicate _____
Though the correlational method is limited in terms of specifying underlying causes, it has several benefits
- it offers clues to underlying causes: The correlational relationships cannot determine cause-and-effect relationships, they may point to possible causal factors that can be followed up an experimental research. For example, evidence of the correlation between smoking and cancer
led to experimental studies with animals that show the exposure to cigarette smoke induced the formation of cancerous lesions in the lungs
-it can identify groups of people at high risk for physical or behavioral problems: knowing that a relationship exist between the positive expectancies of adolescence toward alcohol use in the leader development of problem drinking may direct us toward developing alcoholism prevention efforts that focus on changing attitudes of youngsters before drinking
problems arise
- it increases understanding of relationships between variables or events: such an understanding is one of the major objectives of science. From time to time, we explore such relationships.
In the experimental method, investigators directly explore cause-and-effect relationships by manipulating certain variables, called independent variables, and observing their effects on certain outcomes called dependent variables
______ variables are manipulated, and their effects on the _____ variable or variables are measured
Measures of these variables depend on the independent, or manipulated, variable
Experimenters attempt to hold constant all other factors or conditions to ensure that the ______ variable alone is the cause of the observed effects on the _____ variable
Psychologists use __________ to define variables on the basis of the operations or procedures they use to measure those variables
Operational definitions
-operational definitions establish an objective basis for determining what the variables of interest mean
Experimenters typically use _______ to ensure that the effects of an independent variable are not due to other factors
-in well-designed studies, experimenters use random assignment to place participants randomly in experimental groups or control groups
-Random assignment balances experimental and control groups in terms of the background in personality characteristics of the people who constitute the groups.
-Random assignment gives us confidence
that differences between groups in how they perform on dependent measures are due to the independent variable or variables and not to the characteristics of the people making up the groups
Why is random assignment not always feasible or ethically responsible
Ethical experimenters would never randomly assigned children to be exposed to abuse or neglect to see what affects these experiences might have on their development. They may rely on correlational method is to examine these relationships even though such methods do not necessarily determine cause and effect
An inert pill designed to resemble an active drug
Positive outcomes that reflect a person’s hopeful expectancies about a drug rather than the chemical properties of the drug itself
The placebo effect is an example of the power of ______
Suggestion
-we see this power at work in research evidence that pain patients who are given mere placebos show actual biological changes in parts of the brain involved in processing pain
-taking a placebo may block pain signals to the brain or lead to the release of endorphins,
which are the brains own pain killing chemicals
Placebos typically have stronger effects on ________ than they do on ________
Subjective states, such as pain and negative emotions; objectively measured medical conditions, such as high blood pressure
In drug studies, experimenters attempt to control for expectancy effects by preventing research participants from knowing whether they are receiving the ______ or a ______
Only the participants are kept in the dark
Both the participants and the experimenters are “blinded”- kept uninformed with respect to which participants are receiving the active drug. Keeping the experimenters blind helps prevent their own expectancies from affecting the results
Problem with double blind studies
Participants and experimenters are often able to tell whether a participant received a placebo or an active drug. Active drugs often have telltale side effects that give them away. Still, when conducted properly, the double blind randomized study is among the strongest research methods and is widely considered the gold standard when evaluating new medications
A scientific hypothesis is a predicted outcome informed by a careful review of theory and prior research
Ethical principles in psychological research
Psychologist subscribe to a code of ethics that respect the dignity and welfare of their clients and those who participate in the research studies. This code recognizes that people have a basic right to make their own decisions into exercise choices, including the choice of whether to participate in psychological research. Ethical guidelines also prohibit psychologist from using methods that would harm research participants or clients
People who participate in experiments may be harmed not only by ______ but also by ______
Psychical interventions, such as experimental drugs that have adverse effects; psychological interventions, such as being goaded into aggressive behavior that leads to feelings of guilt or shame. Invasions of privacy are another concern
Today, nearly all institutions in which biomedical and behavioral research is conducted, such as hospitals, colleges, and research foundations, have
Ethics review committees
-these committees, which are generally called institutional review boards, are usually composed of professionals and laypeople
-they must put their stamp of approval on all research proposals before the research can be carried out at their institutions
-the committees
review proposals to see that they comply with ethical guidelines and advise researchers concerning the potential harm of their proposed methods.
-in cases in which research participants may experience harm or discomfort, the IRB must weigh the potential benefits of the research against the potential harm
One of the foremost ethical requirements is that investigators obtain _________ from research participants before they begin participating in the study
Informed consent
-this means that participants must be given enough information about the study’s methods and purposes to make an informed decision about whether they wish to participate
APA conditions for deceptive practices in research
Research is justified by its scientific, educational or practical value; that no non deceptive alternative research strategy is possible; that research participants are not misled about any research that can reasonably be expected to result in physical harm or severe emotional distress; and that participants receive an explanation of the deception at the earliest time it is feasible to do so
Psychologists must protect the ______ of the records of research participants and of the clients they treat, or their right to privacy
Confidentiality
-there are some situations when laws require psychologists to disclose confidential information acquired in research or clinical practice, as when a participant or a theory client threatens to do physical harm to someone else
Ethical guidelines also extend to the use of _____ in psychological research
_____ are the cells in the body that are specialized for transmitting information or messages in the form of electrical impulses
Each neuron is a single cell consisting of a _____, ______, and _____
The ____ is the main body of the cell
Soma
-it houses the cell nucleus, which contains the cell’s genetic material and carries out the metabolic or life sustaining functions of the cell
A long cable that projects trunklike from the soma and conducts outgoing messages to other neurons
A neuron or nerve cell consists of a cell body, or soma, which houses the cells nucleus; an axon, which carries the neural message; and dendrites, which receive messages from adjacent neurons
-terminal buttons are swellings at the end of the axon from which neurotransmitter molecules are released to ferry the message to other neurons
-axons of many neurons are covered with a myelin sheath, which is a type of insulating layer that helps speed transmission of neural
impulses
Axons may branch off like the stems of plants, fanning out in different directions. At the end of these branches are knoblike swellings called
Terminal buttons
-it is here that chemicals called neurotransmitters are stored and released. These chemicals are synthesized in the soma and ferry outgoing messages to neighboring neurons at
the synapse, the tiny gap that separates one neuron from another and serves as a connection point between neurons
Treelike structures that protect from the soma
-have receptor sites that enable them to receive neurotransmitters released by neighboring neurons
-each neuron May receive messages from thousands of other neurons through its dendrites
The nervous system has three types of neurons
Sensory neurons, motor neurons, and interneurons
-these different types play specialized roles in the nervous system
Transmit information about the outside world to the spinal cord and brain
-this information first registers on your sensory organs
-sensory neurons also carry information from your
muscles and inner organs to your spinal cord and brain
-also called efferent neurons
-convey messages from the brain and spinal cord to the muscles that control the movements of your body
-they also convey messages to your glands, causing them to release hormones
Chemical substances that help regulate bodily processes
-also
called associative neurons
-the most common type of neuron in the nervous system
-connect neurons to neurons
-in the spinal cord, they connect sensory neurons to motor neurons
-in the brain they form complex assemblages of interconnected nerve cells that process information from sensory organs and control higher mental functions such as planning and thinking
A neuron is not the same thing as a
A nerve is a bundle of axons from different neurons. An individual nerve contains more than a million axons.
-although individual axons are microscopic, a nerve may be visible to the naked eye
-the cell bodies of the neurons that contain the axons are not part of the nerve itself
Neurons are not the only cells in the nervous system. Far more numerous are small cells called _______ that act as a kind of glue to hold neurons together
Glial cells
-the word glial is derived from the Greek word for glue
-glial cells also support and nourish neurons in a number of ways, such as by removing their waste products and may even assist them in communicating with one another
-formed by glial cells
-fatty layer of cells that
acts as a protective shield on many axons
-the insulation provided by the myelin sheath helps speed transmission of neural impulses, which allows muscles to move more efficiently and smoothly
Myelinated axons resemble a string of sausages that are pinched at various points, creating gaps called
Nodes of ranvier
-the neural impulse appears
to jump from node to node as it speeds down the axon
A chronic and often crippling disease of the central nervous system, affecting about one in one thousand adults, in which the body’s own immune system attacked and eventually destroys the myelin sheath.
-the loss of myelin slows the transmission of nerve impulses, leading to a range of symptoms; in most severe cases, the person loses the ability to speak, walk, write, or breathe
Both inside and outside the neuron are electrically charged atoms and molecules called
Ions
-ions have either a positive or negative charge
-the movements of ions across the cell wall, or cell membrane, cause electrochemical changes in the cell that generate an electrical signal to travel down the cells axon in the form of a neural impulse
-the most important ions in this process are two types of positively charged ions, sodium ions and potassium ions
-the movement of ions through the cell membrane is controlled by a series of gates that open to allow ions to enter the cell and close to shut them out
When a neuron is at rest, the gates that control the passage of sodium ions are
A greater concentration of
positively charged sodium ions remain outside the cell, causing the cell to have a slightly negative charge relative to the surrounding fluid
-the resting potential of a neuron is about -70 millivolts
-a neuron in the resting state holds a store of potential energy that can be used to generate a neural impulse in response to stimulation
When a cell is stimulated, usually by neurotransmitters released from adjoining neurons, sodium gates at the base of the axon
Open
-positively charged sodium ions from the surrounding fluid then rush in, which causes the area inside the membrane at the point of excitation to become less negatively charged
-this process is called depolarization
-when stimulation is sufficiently strong, as when enough of a neurotransmitter is present, depolarization quickly spreads along the cell
membrane
-as this wave of depolarization reaches a critical threshold, the neuron abruptly shifts from a negative charge to a positive charge of about 140 mV
The sudden reversal of electrical charge is called an _______, or neural impulse
Action potential
-the action potential typically begins at the juncture between the soma and the
axon, or the axon hillock
-it then shoots down the entire length of the axon as a wave of changing electrical charges
-we refer to this as the firing of a neuron
Once an action potential reaches the end of an axon, it causes the release of neurotransmitters from the terminal buttons that
Carry the neural message to the next neuron
A neuron will fire completely (generate an action potential) if sufficient stimulation is available, or it will not fire; there is no halfway point
Different axons generate action potentials of different speeds depending on
Their thickness (thicker the axon, faster the speed) and whether or not they are covered with a myelin sheath
For about one thousandth of a second after firing, a neuron prepares to fire again: sodium gates along the cell membrane close to prevent further influx of positively charged sodium ions into the cell, cell pumps out positively charged ions, mostly potassium ions, and the neurons negatively charged resting potential is restored
-then the cell restores the electrochemical balance by pumping
out sodium ions and drawing in some potassium ions, making it possible for another action potential to occur
-during the time these changes are occurring the neuron is temporarily incapable of firing
Neurons are separated by the tiny fluid filled gap called a ____, which measures less than a millionth of an inch across
Because neural impulses or messages cannot jump from neuron to neuron, they need to be transferred by _______
Neurotransmitters, the chemical agents or messengers that carry the message across the synapse
Each type of neurotransmitter has a particular chemical structure. It fits into only one kind of _______, like a key fitting into a lock
When neurotransmitters dock at receptor sites;
-lock into place and cause chemical changes in the receiving neuron
-these changes either have an excitatory or inhibitory effect
Make an action potential more likely to occur
Make an action potential less likely to occur
Several processes that prevent excitatory neurotransmitters from continuing to stimulate a receiving cell
-reuptake: neurotransmitters not taken up by the receiving cell are reabsorbed by their vesicles to be used again
-enzymes in the synapse break down neurotransmitters, which are then eliminated from the body in the urine
-terminal buttons
release neuromodulators, chemicals that either increase or decrease the sensitivity of the receiving neuron to neurotransmitters
Sometimes receptor sites allows too many neurotransmitters to dock, or they don’t accept neurotransmitters properly:
-excess or deficits of particular neurotransmitters in the brain, or irregularities in how they
function, are associated with many disorders
-irregularities in neurotransmitter functioning are linked to eating disorders, depression, and schizophrenia
Drugs or chemicals that block the actions of neurotransmitters by occupying their receptor sites are called
Antagonists
-by locking into these receptor sites, antagonists prevent
transmission of the messages the neurotransmitter carries
-ex) dopamine- irregularities in how the brain uses dopamine may help explain the development of schizophrenia, a severe mental disorder involving a break with reality