Introduction To Psychology October 26th The APA defines Psychology as “a diversediscipline, grounded in science, but with nearly boundless applications in everyday life. Some psychologists do basic research, developing theories and testing them through carefullyhoned research methods involving observation, experimentation and analysis. Other psychologists apply the discipline’s scientific knowledge to help people, organizations and communities function better.”
Psychology is a Science• Psychology uses scientific methods to study the brain, the mind, and mental states in order to create theories: cognitive behaviorism, behaviorism, humanism, existential humanism, nature, nurture, psychosexual, object relations, psychosocial, Adlerian, physiological/genetic/evolutionary and multiculturalism.
What is the Brain• The brain is the portion of the central nervous system in vertebrates (animals with bones) that lies within the skull.
The human mind• The human mind is the portion of the brain where we think and make decisions. It is the area where we perceive things and create a response to them.
What are Mental States• A mental state is a mental condition in which the qualities of a state are relatively constant even though the state itself may be dynamic, e.g. a manic state, a paranoid state, a depressed state, an anxious state.
Psychology Studies Human and Animal Behavior• Many problems in human society are often related to the interaction of environment and behavior or genetics and behavior.• The fields of socio-ecology and animal behavior deal with the issue of environment behavioral interactions both at an evolutionary level and a proximate level.• Social scientists study both human and animal behavior as a framework in which to interpret human society and to understand possible causes of societal problems.
Psychologist Study and Research• The character traits and associated behavior and activities of a person or group of people.• Actions and words used to influence a person or group to behave in different ways.• A random sample group of people are a group of individuals who could be used in a research testing situation.• Every person in the area under study has an equal chance of being included in the sample.• The process of selecting this sample on the basis of chance is called randomization.
Research• An example of research study that would correlate a theory might be a study between enrollment in a class and rate my professor evaluations, and the correlation between the demand for a product and its price.• Correlations are useful because they can indicate a predictive relationship that can be used in understanding the brain, the mind, mental states, behavior, stimulus and response.
Research• Statistics is a numerical value or function used to describe a sample or population• In statistical research, dependence refers to any statistical relationship (dependency) between two or more random variables or two or more sets of data.• Correlation refers to any of a broad class of statistical relationships involving dependence.
Psychologist are• To use research to understand the brain, the mind, mental states, and behavior.• To use variables to predict human brain activity, belief systems, mental states, character development, and behavior.• To describe human behavior in a way that will categorize a clear and accurate diagnosis.
Industrial Psychologist/Organizational Psychologist• Industrial psychologists study the behavior of employees in a work setting.• The workplace is a social system, the application of industrial psychology is useful in understanding its complexity.• They analyze the way a person works, their skills, duties, obligations, and general satisfaction with their job on a day-to-day basis.
Industrial/Organizational Psychologist• This information is extremely helpful to company overseers who must create training programs, feedback and rewards systems, and make hiring decisions as well as engage in recruitment practices.• Companies use industrial psychologists to train their own staff so that the organizations can run smoothly and at peak capacity.
Industrial/Organizational Psychologist• One of the most interesting aspects of industrial psychology is how employee behavior affects others individuals on the job and organization in general. Industrial psychology can be used to reduce counterproductive behavior, enhance team effectiveness, and boost morale. It is also vital in conflict resolution. Many individuals find the brunt of their work dissatisfaction rooted in their relationships with managers and colleagues.
Clinical Psychologist• Clinical Psychologist are concerned with the assessment, diagnosis, treatment, and prevention of mental disorders.• While some clinical psychologists specialize in treating severe psychological disorders, such as schizophrenia and depression, many others may help people deal with personal issues, such as divorce or the death of a loved one.• Clinical psychologists provide an opportunity to talk and think about things that are confusing or worrying, offering different ways of interpreting and understanding problems and situations. They are trained to use a variety of approaches aimed at helping individuals, and the strategies used are generally determined by the specialty they work in.
Counseling Psychologist• Facilitates personal and interpersonal functioning across the life span with a focus on emotional, social, vocational, educational, health-related, developmental, and organizational concerns. Through the integration of theory, research, and practice, and with a sensitivity to multicultural issues, this specialty encompasses a broad range of practices that help people improve their well-being, alleviate distress and maladjustment, resolve crises, and increase their ability to live more highly functioning lives. Counseling psychology is unique in its attention both to normal developmental issues and to problems associated with physical, emotional, and mental disorders.
Counseling and Psychotherapy• Counseling is appropriate for the lower level patient who cannot tolerate the therapist’s being neutral and therefore is not a candidate for psychotherapy. When counseling, the therapist can advise, direct, support, suggest medications.• Therapeutic intervention is appropriate for mid and high level patients. The essence of the psychotherapy with mid to high level patients is the therapist’s identification of the clinical vicissitudes (state of being changeable).• therapeutic technique is bringing to the center of the patient’s attention firmly and empathetically the denied maladaptive self-destructive aspect of the defenses that protect their mental state/self.
Counseling and TherapyThink of the following:• With lower level patients self-activation leads to separation anxiety and abandonment depression which leads to self destructive defenses.• Self-activation is precipitated by real later life situations that require self assertion, autonomous functioning and/or by events that involve separation.• These events interrupt the self destructive defenses and the patient begins to experience the abandonment depression and then defends by giving up self assertion and activating self destructive defenses whose symptoms can vary from obesity to anorexia, from clinging to others to distancing from others, from sexual promiscuity to the avoidance of sex, from alcoholism to drug addiction.• There are three clinical types based on the patient’s capacity to function: lower level, mid level, and high level
APA Mission Statement• “The mission of the APA is to advance the creation, communication and application of psychological knowledge to benefit society and improve people’s lives.”• This is also the mission of this class.
Abnormal Psychology• Psychologist use a Subjective, Objective, Assessment Plan (SOAP) to diagnose a patient.• Symptoms — subjective — what apatient describes about their condition and/orcomplain about.• Signs — objective — what a Psychologist can sense, i.e. hear, see, smell, and process when listening to the patient.
DiagnosisKnowledge of:• Diagnostic and Statistical Manual of Mental Disorders DSM-IV-TR Fourth Edition (Text Revision) the APA approved text for diagnosis.• Knowledge of research on appropriate, effective, and efficient treatment plan
Multi-axial Diagnosis• 5-axis diagnostic system is a multi-axial system that facilitates comprehensive and systematic evaluation of the patient and takes into account:• Axis I: Psychological diagnosis(s)• Axis I diagnosis(s) are called the primary diagnosis. If there is more than one primary diagnosis (dual diagnosis, comorbid diagnoses) the primary one is mentioned first.
Some Axis I Diagnosis• Some primary diagnosis ADHD, eating disorders , Organic Mental Disorders ( Dementia arising from Alzheimer’s, basically anything that has a physical medical cause, i.e. a brain tumor), Psychoactive Substance Use Disorders, Psychosis (schizophrenia,) Mood Disorders ( depression, bi-polar, Anxiety/ Neuroses ( panic disorder, phobias, OCD, PTSD,) Somatoform Disorders, Dissociative Disorders (Multiple Personality Disorder, psychogenic fugue), Sexual Disorders (exhibitionism, fetishism) Sleep Disorders
Axis II• Developmental diagnoses and diagnoses first diagnosed in infancy or childhood, e.g., developmental delays, mental retardation, autism, language and speech disorders• Personality Disorders, e.g., paranoid, avoidant, obsessive compulsive, passive aggressive, histrionic, borderline, narcissism, dependence, schizotypal personality
Axis II• These diagnoses are difficult to make and are often only made after several visits.• The listing of personality disorders and mental retardation on Axis II rather than Axis I ensures that consideration is given to the possible presence of these conditions which might be overlooked when attention is focused on the usually more florid (a blatant or highly disorganized state) Axis I disorders, i.e., the primary disorder.
• An Axis II diagnosis should not be made while the patient is suffering from an Axis I diagnosis. For example, a person with depression should not be diagnosed with a personality disorder while the depression is still present; depression does not allow a true evaluation of a person’s personality.• In this case, the Axis II diagnosis is deferred.
Axis III• All physical diseases are mentioned here, whether the disease symptoms are related to the psychiatric disorders or not.• These general medical conditions are potentially relevant to the understanding or management of the individual’s mental disorder.• In some cases it is clear that the general medical condition is directly related to the development or worsening of mental symptoms.• When a mental disorder is judged to be a direct physiological consequence of the general medical condition it should be diagnosed on Axis I and the general medical condition should be recorded on both Axis I and Axis III.
• For example, when hypothyroidism (thyroid gland does not make enough thyroid hormone) is a direct cause of depressive symptoms, the designation on Axis I is mood disorder due to hypothyroidism with depressive features, and the hypothyroidism is listed again on Axis III.• Some general medical conditions may not be directly related to the mental disorder, but have important prognostic or treatment implications. For example:• when the diagnosis on Axis I is major depressive disorder and on Axis III is arrhythmia( abnormal heart rhythm), the choice of pharmacotherapy for the depressive disorder is influenced by the arrhythmia.
Axis IV• Axis IV: Psychological stress factors affecting the patient, e.g., stressors, past and present, which have an influence on the patient at the time of the evaluation.• These factors may include situations dating from childhood up to the• present day.• Possible psychosocial or environmental problems include: negative life events, environmental difficulties or deficiencies, familial or other interpersonal stressors, inadequate social support or personal resources, problems relating to the context in which a person’s difficulties have developed.
Axis V: Global Functioning of the Patient• This gives a broad evaluation of the individual’s ability to cope with their present life situation and can also be used as a measure of the need for hospital admission. This information is useful in planning treatment and measuring its impact as well as in predicting outcome.• The Global Assessment of Functioning (GAF) scale can be used to quantify this• level of functioning.• The GAF scale was developed specifically to rate psychological, social and occupational functioning global functioning of the patient.
• The Global Assessment of Functioning (GAF) is a numeric scale• (0 through 100) used by mental health clinicians and physicians to subjectively rate the social, occupational, and psychological functioning of adults, e.g., how well or adaptively one is meeting various problems-in-living. The score is often given as a range, as outlined below:• 91 - 100 Superior functioning in a wide range of activities, lifes problems never seem to get out of hand, is sought out by others because of his or her many positive qualities. No symptoms• . 81 - 90 Absent or minimal symptoms (e.g., mild anxiety before an exam), good functioning in all areas, interested and involved in a wide range of activities, socially effective, generally satisfied with life, no more than everyday problems or concerns (e.g., an occasional argument with family members).• 71 - 80 If symptoms are present, they are transient and expectable reactions to psychosocial stressors (e.g., difficulty concentrating after family argument); no more than slight impairment in social, occupational, or school functioning (e.g., temporarily falling behind in schoolwork).
• 61 - 70 Some mild symptoms (e.g., depressed mood and mild insomnia) OR some difficulty in social, occupational, or school functioning (e.g., occasional truancy, or theft within the household), but generally functioning pretty well, has some meaningful interpersonal relationships. 51 - 60 Moderate symptoms (e.g., flat affect and circumstantial speech, occasional panic attacks) OR moderate difficulty in social, occupational, or school functioning (e.g., few friends, conflicts with peers or co-workers). 41 - 50 Serious symptoms (e.g., suicidal ideation, severe obsessional rituals, frequent shoplifting) OR any serious impairment in social, occupational, or school functioning (e.g., no friends, unable to keep a job).
• 31 - 40 Some impairment in reality testing or communication (e.g., speech is at times illogical, obscure, or irrelevant) OR major impairment in several areas, such as work or school, family relations, judgment, thinking, or mood (e.g., depressed man avoids friends, neglects family, and is unable to work; child frequently beats up younger children, is defiant at home, and is failing at school).• 21 - 30 Behavior is considerably influenced by delusions or hallucinations OR serious impairment, in communication or judgment (e.g., sometimes incoherent, acts grossly inappropriately, suicidal preoccupation) OR inability to function in almost all areas (e.g., stays in bed all day, no job, home, or friends)• 11 - 20 Some danger of hurting self or others (e.g., suicide attempts without clear expectation of death; frequently violent; manic excitement) OR occasionally fails to maintain minimal personal hygiene (e.g., smears feces) OR gross impairment in communication (e.g., largely incoherent or mute).• 1 - 10 Persistent danger of severely hurting self or others (e.g., recurrent violence) OR persistent inability to maintain minimal personal hygiene OR serious suicidal act with clear expectation of death.
Disorders Usually First Diagnosed in Infancy, Childhood, or Adolescence• monitoring of children and adolescents with language and learning disorders (LLDs). LLDs are among the most common developmental disorders the clinician is likely to encounter. About 50% of children with an LLD also have a comorbid Axis I psychiatric disorder.• The diagnosis of an LLD requires a discrepancy, based on age and intelligence, between potential and achievement.• The clinician collaborates with parents and school personnel to clarify the diagnosis, implement appropriate treatment and remediation, and monitor progress.• The clinician is instrumental in identifying and treating comorbid conditions, including the determining the appropriateness of medication.• Long-term prognosis depends on the type and severity of the language/learning disorder, the availability of remediation, and the presence of a supportive family and school environment.• Key Words: Language, learning, disorders, disabilities, diagnosis, treatment, children, adolescents, practice parameters, guidelines.
PL 94-142/ Individual with Disabilities Education Act (IDEA)• In 1975, Congress passed Public Law 94-142 (Education of All Handicapped Children Act), now codified as IDEA (Individuals with Disabilities Education Act). In order to receive federal funds, states must develop and implement policies that assure a free appropriate public education (FAPE) to all children with disabilities.
IDEA• IDEA (Individuals with Disabilities Education Act) was created to provide full legal rights and services for students with disabilities to receive an appropriate education in school communities. These services are rendered on the basis of a students Individualized Education Program (IEP)
IDEA• (IDEA) is an important tool for providing Free Appropriate Public Education (FAPE) to students with disabilities. IDEA provides special education to eligible students with disabilities in the least restrictive learning environment.• These services are provided to children between 3-21 years of age. To avail the benefits of IDEA, a child must meet the eligibility criteria in one of thirteen qualifying disabilities. To qualify for IDEA a child must have a disability that creates hindrance in his or her education. Thus eligibility for IDEA depends upon the severity of the impairment of a child.
• Different categories of disabilities that are included in IDEA are autism, deaf/blind, specific learning disabilities, hearing impaired, deafness, mental retardation, orthopedic impairment, speech or language impairment, visual impairment, traumatic impairment and other health problems.• It includes mental illness, but not behavioral issues.
Other Handicap Impaired (OHI)• Other health impairment means having limited strength, vitality or alertness, including a heightened alertness to environmental stimuli, that results in limited alertness with respect to the educational environment, that—(i) Is due to chronic or acute health problems such as asthma, attention deficit disorder or attention deficit hyperactivity disorder, diabetes, epilepsy, a heart condition, hemophilia, lead poisoning, leukemia, nephritis (is an inflammation of one or both kidneys), rheumatic fever, and sickle cell anemia; and (ii) Adversely affects a child’s educational performance.
OHI• Generally speaking, analysis of OHI eligibility first considers the child’s health condition and its general effects on the child, then looks separately at the disability’s effect on the child’s educational performance.
Experimental Research October 29thResearch designs can be used where:• There is time priority in a causal relationship (cause precedes effect),• There is consistency in a causal relationship (a cause will always lead to the same effect), and• The magnitude of the correlation is great.
Cause and Effect• Causality is the relationship between an event (the cause) and a second event (the effect), where the second event is understood as a consequence (end result) of the first.
Hypothesis• A conditional proposition or a premise used in an argument. The antecedent of a conditional proposition is the “if” and the consequent is the “then”. A mere assumption or guess.
Dependent and Independent Variable• The terms "dependent variable" and "independent variable" are used to distinguish between two types of quantities being considered (hypothesis).• separating them into those available at the start of a process (independent variables) and those being created by it (dependent variables).• Dependent variables are dependent on the independent variables.
Experimental Group• A group of subjects exposed to the independent variable of an experiment (compare control group). Typically, the experimental group is treated with the independent variable to test an experimental hypothesis.
Control Group• The resultant effect, measured by a dependent variable, is compared with the control group. The control group is practically identical to the experimental group, although the experimental group is changed according to some key variable of interest, while the control group remains constant during the experiment. Each field develops their own specific, important controls.
random assignment• Random assignment refers to the use of chance procedures in psychology experiments to ensure that each participant has the same opportunity to be assigned to any given group. Study participants are randomly assigned to different groups, such as the experimental group or treatment group. Random assignment might involve such tactics as flipping a coin, drawing names out of a hat or assigning random numbers to participants.
Experimenter Bias• Experimenters bias is the phenomenon in experimental science by which the outcome of an experiment tends to be biased towards a result expected by the human experimenter. The inability of a human being to remain completely objective is the ultimate source of this bias
double-blind• Double-blind trials describe a study in which both the investigator or the participant are unaware of (blind to) the nature of the experiment.• Double-blind trials are thought to produce objective results, since the expectations of the researcher and the participant about the experiment do not affect the outcome.
placebo• Some participants (unknown to the investigator and the participant) are given a substance, behavior, cue, expectation that has no effect on the study. This is called a placebo.• Some given a placebo may respond to meet the perceived expectations of the investigator this phenomenon is called the placebo effect.
Example• The independent variable is typically the variable representing the value being manipulated or changed and the dependent variable is the observed result of the independent variable being manipulated. For example concerning nutrition, the independent variable of daily vitamin C intake (how much vitamin C one consumes) can influence the dependent variable of life expectancy (the average age one attains). Over some period of time, scientists will control the vitamin C intake in a substantial group of people. One part of the group will be given a daily high dose of vitamin C, and the remainder will be given a placebo pill (so that they are unaware of not belonging to the first group) without vitamin C. The scientists will investigate if there is any statistically significant difference in the life span of the people who took the high dose and those who took the placebo (no dose). The goal is to see if the independent variable of high vitamin C dosage has a correlation with the dependent variable of peoples life span. The designation independent/dependent is clear in this case, because if a correlation is found, it cannot be that life span has influenced vitamin C intake, but an influence in the other direction is possible.
Mean, Mode, Median, Range• The "mean" is the "average" youre used to, where you add up all the numbers and then divide by the number of numbers.• The "median" is the "middle" value in the list of numbers. To find the median, your numbers have to be listed in numerical order, so you may have to rewrite your list first.• The "mode" is the value that occurs most often. If no number is repeated, then there is no mode for the list.• The "range" is just the difference between the largest and smallest values
standard deviation; statistical significance• To understand standard deviation we have to start with the idea of a normal distribution or bell curve The midpoint of the bell curve will be the average value. So take for example the height of males in the U.S. If we graphed it, the curve would have a bell shape.
• The most common value would be near the top of the bell shape and the least common values would be at the tail ends of the bell curve. If you drew a line that cut the bell in half starting at the peak of the bell and going down then that line would represent the average height, around 5’10″.
• Dark blue is one standard deviation from the mean. For the normal distribution, this accounts for about 68% of the set, while two standard deviations from the mean (medium and dark blue) account for about 95%, and three standard deviations (light, medium, and dark blue) account for about 99.7%.
• Now the standard deviation is a measure of how much variation there is in the population. If the standard deviation is small then the bell curve will be a very tall thin bell meaning everyone is pretty close to average. Whereas if the standard deviation is large then the bell curve is a short fat bell meaning everyone is fairly unique and not too close to the average.
• There is an important relationship between the standard deviation and the percentage of the population near the average. It is always the case that if you go one standard deviation to the left and to the right of the average value then you will cover 68% of the population. If you go two standard deviations in each direction you will cover 95% of the population. So in the height example, if the standard deviation is 3 inches then 68% of the male population will be between 5′ 7″ and 6’1″ and if you go two standard deviations then 95% of the male population will be between 5′ 4″ and 6’4″.
• You’ll often see this idea misinterpreted in media reports on polling results. Suppose candidate A is ahead of candidate B in a poll by 52 – 48% with a margin of error of 2%. The media will report that the difference in the poll falls within the margin of error and therefore the race is a dead heat. This is absolutely false and shows they don’t understand standard deviations and normal distribution. Since the margin of error is the same as 2 standard deviations then there is a 95% chance that candidate A will end up with between 50 and 54% of the vote. This isn’t a dead heat. There is a 95% chance that candidate A will get at least 50% of the vote. Candidate A is clearly winning according to the polls.
• It is important to keep in mind that everything we said is based on the assumption of a normal distribution or a bell curve. While there are many famous examples of normal distributions in nature there are also plenty of examples of things that don’t follow a normal distribution. The mathematics gets a little trickier when there isn’t a normal distribution. So people often make the mistake of just assuming that something has a normal distribution and this can lead to errors as we discussed in the post about the black swan.
Statistical Significance• The concept of statistical significance is very important in understanding if a result is valid or not and yet its meaning is almost always misinterpreted. This post will attempt to clarify what it means to have a result that is “statistically significant”.
• When reading scientific papers you will often see that the experimenter has run some statistical test (usually a t-test) and reported that the results were significant at a level of p < .05. What this means is that there is a less than 5% chance that the results were just due to randomness. The flip side of that is that there is a 95% chance that the difference in the variable between the test group and the control group is a real difference and not just due to chance.
• You see, the test that was being run is basically a test that compares your hypothesis (that there is a difference between the test group and the control group) to what is called the “null” hypothesis (that there is no difference between the test group and the control group and the result you are seeing is just due to random chance probably caused by a sample that is either too small or poorly chosen).
• This might be a little clearer with an example. Suppose I did an experiment to test the idea that left handed people are smarter than right handed people and I selected 100 left handed people and 100 right handed people at random and gave them an IQ test. The results show that the average IQ of the left handed people was 120 and the average IQ of the right handed people was 108. When I run a t-test on the data I get p = .04 or a significance level of 96%. This doesn’t mean that if I select 1 left handed person and 1 right handed person from a crowd that there is a 96% chance that the difference in their IQ will be 12.
• What it means is that there is a 96% chance that difference in IQs between left handed and right handed people is real and that you will see this difference in any sample that is large enough or well selected. The difference won’t necessarily be 12 points as in the current experiment but there will be a difference in the favor of the left handed people.
Correlational Research (prediction)• Correlational studies are used to look for relationships between variables. There are three possible results of a correlational study: a positive correlation, a negative correlation, and no correlation. The correlation coefficient is a measure of correlation strength and can range from –1.00 to +1.00.
Direction: Both variables increase or decrease at the same time.• Positive Correlations:. A correlation coefficient close to +1.00 indicates a strong positive correlation.• Negative Correlations: Indicates that as the amount of one variable increases, the other decreases (and vice versa). A correlation coefficient close to -1.00 indicates a strong negative correlation.• No Correlation: Indicates no relationship between the two variables. A correlation coefficient of 0 indicates no correlation.
Strength correlation coefficient r• In statistics, dependence (the result is dependent on the relationship between the variables) refers to any statistical relationship between two random variables or two sets of data. Correlation refers to any statistical relationships involving dependence (occurring because of the relationship)• An examples of dependent phenomena include the correlation between the physical statures of parents and their offspring.• Correlations are useful because they can indicate a predictive relationship that can be exploited (statistical term) in practice.• An example of an electrical utility may produce less power on a mild day based on the correlation between electricity demand and weather. In this example there is a causal relationship, because extreme weather causes people to use more electricity for heating or cooling; however, statistical dependence is not sufficient to demonstrate the presence of such a causal relationship.
• In loose usage, correlation can refer to any departure of two or more random variables from independence to dependence.
Perfect Correlation• Perfect positive correlation (a correlation co- efficient of +1) implies that as one variable moves, either up or down, the other variable will move in the same direction.
Negative Correlation 0.0• a zero correlation is a score which shows that there is no relationship between two or more variables. A correlation of –1 indicates a perfect negative correlation, meaning that as one variable goes up, the other goes down.
Correlation does not imply causation"ignoring a common cause" and questionablecause are phrases used in science and statisticsto emphasize that correlation between twovariables does not automatically imply that onecauses the other, but rather a possible cause orareas for further investigation; in other words,correlation can be a hint
Biology and Behavior
Neuron: overview• A neuron also known as a nerve cell• It is an electrically excitable cell that processes and transmits information by electrical and chemical signaling• Chemical signaling occurs via synapses, specialized connections with other cells• Neurons connect to each other to form networks• Neurons are the core components of the nervous system, which includes the brain, spinal cord, and peripheral ganglia.
A number of specialized types of neurons exist:• sensory neurons respond to touch, sound, light and numerous other stimuli affecting cells of the sensory organs that then send signals to the spinal cord and brain.• Motor neurons receive signals from the brain and spinal cord, cause muscle contractions, and affect glands.• Interneurons connect neurons to other neurons within the same region of the brain or spinal cord.
• Dendrites are the branches of neurons that receive signals from other neurons and pass the signals into the cell body• A cell may have hundreds or thousands of dendrites, but may have only one axon. The dendrites carry signals from other neurons into the soma, whereas the axon carries a single signal from the soma to the next neuron.• Dendrites are the branches of neurons that receive signals from other neurons and pass the signals into the cell body• A cell may have hundreds or thousands of dendrites, but may have only one axon. The dendrites carry signals from other neurons into the cell body whereas the axon carries a single signal from the cell body to the next neuron.• The movement of the charged ions in the dendrite causes an electrical current, which spreads to the cell body briefly before being restored to normal.
• Neurons have specialized projections called dendrites and axons. Dendrites bring information to the cell body and axons take information away from the cell body.• Information from one neuron flows to another neuron across a synapse. The synapse contains a small gap separating neurons. The synapse consists of:• a presynaptic ending that contains neurotransmitters, mitochondria and other cell organelles• a postsynaptic ending that contains receptor sites for neurotransmitters• a synaptic cleft or space between the presynaptic and postsynaptic endings.
Dendrite• A dendrite from one neuron and an axon from another neuron meet at a synapse, which is a very narrow gap between the two cells. When electrical impulses reach the end of an axon, they trigger the release of special chemicals called neurotransmitters from the axon. These chemicals cross the synapse to the dendrite, where they trigger the flow of ions into or out of the cell.
cell body (soma)• the part of a cell that contains the nucleus and surrounding cytoplasm exclusive of any projections or processes, such as the axon and dendrites.
axon• An axon is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma.
myelin• the myelin sheath, around the axon of a neuron. It is essential for the proper functioning of the nervous system. Myelin is an outgrowth of a type of glial cell.
resting potential• The resting potential of a cell occurs when the cell has a negative value, which by convention means that there is excess negative charge inside compared to outside.• The resting potential is mostly determined by the concentrations of the ions in the fluids on both sides of the cell membrane and the ion transport proteins that are in the cell membrane.
• Neurons send messages electrochemically. This means that chemicals cause an electrical signal. Chemicals in the body are "electrically-charged" -- when they have an electrical charge, they are called ions. The important ions in the nervous system are sodium and potassium (both have 1 positive charge, +), calcium (has 2 positive charges, ++) and chloride (has a negative charge, -). There are also some negatively charged protein molecules. It is also important to remember that nerve cells are surrounded by a membrane that allows some ions to pass through and blocks the passage of other ions. This type of membrane is called semi-permeable.
• Action potentials are caused by an exchange of ions across the neuron membrane. A stimulus first causes sodium channels to open. Because there are many more sodium ions on the outside, and the inside of the neuron is negative relative to the outside, sodium ions rush into the neuron. Remember, sodium has a positive charge, so the neuron becomes more positive and becomes depolarized. It takes longer for potassium channels to open. When they do open, potassium rushes out of the cell, reversing the depolarization. Also at about this time, sodium channels start to close. This causes the action potential to go back toward -70 mV (a repolarization). The action potential actually goes past -70 mV (a hyperpolarization) because the potassium channels stay open a bit too long. Gradually, the ion concentrations go back to resting levels and the cell returns to -70 mV.
• When a neuron is not sending a signal, it is "at rest."• When a neuron is at rest, the inside of the neuron is negative relative to the outside.• The concentrations of the different ions attempt to balance out on both sides of the membrane, they cannot because the cell membrane allows only some ions to pass through channels (ion channels).• At rest, potassium ions (K+) can cross through the membrane easily. Also at rest, chloride ions (Cl-)and sodium ions (Na+) have a more difficult time crossing. The negatively charged protein molecules (A-) inside the neuron cannot cross the membrane.• There is a pump that uses energy to move three sodium ions out of the neuron for every two potassium ions it puts in.• When all these forces balance out, and the difference in the voltage between the inside and outside of the neuron is measured, you have the resting potential. The resting membrane potential of a neuron is about -70 mV (mV=millivolt) - this means that the inside of the neuron is 70 mV less than the outside. At rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron.
action potential (all-or-none law)• The resting potential tells about what happens when a neuron is at rest. An action potential occurs when a neuron sends information down an axon, away from the cell body. Neuroscientists use other words, such as a "spike" or an "impulse" for the action potential. The action potential is an explosion of electrical activity that is created by a depolarizing current. This means that some event (a stimulus) causes the resting potential to move toward 0 mV. When the depolarization reaches about -55 mV a neuron will fire an action potential. This is the threshold. If the neuron does not reach this critical threshold level, then no action potential will fire. Also, when the threshold level is reached, an action potential of a fixed sized will always fire...for any given neuron, the size of the action potential is always the same. There are no big or small action potentials in one nerve cell - all action potentials are the same size. Therefore, the neuron either does not reach the threshold or a full action potential is fired - this is the "ALL OR NONE" principle.
synaptic vesicles• synaptic vesicles (or neurotransmitter vesicles) store various neurotransmitters that are released at the synapse
neurotransmitters• Chemicals, called neurotransmitters, are released from one neuron at the presynaptic nerve terminal. Neurotransmitters then cross the synapse where they may be accepted by the next neuron at a specialized site called a receptor. The action that follows activation of a receptor site may be either depolarization or hyperpolarization• A depolarization makes it MORE likely that an action potential will fire; a hyperpolarization makes it LESS likely that an action potential will fire.
Acetylcholine• Acetylcholine is a neurotransmitter that slows the heart rate when functioning as an inhibitory neurotransmitter. However, acetylcholine also behaves as an excitatory neurotransmitter at neuromuscular junctions.
sensory neuron• Sensory neurons are activated by sensory input (vision, touch, hearing, etc.), and send projections into the central nervous system that convey sensory information to the brain or spinal cord. Unlike neurons of the central nervous system, whose inputs come from other neurons, sensory neurons are activated by physical modalities such as light, sound, and temperature.
motor neuron• A motor neuron is a type of cell in the nervous system that directly or indirectly controls the contraction or relaxation of muscles, which in most cases leads to movement.• Motor neurons are efferent neurons.• Efferent neurons carry information from the central nervous system to muscles and other systems• afferent neurons, or sensory neurons, carry information from sensory organs and tissues such as eyes and skin back to the central nervous system.