Tutorial and Solution - Psychology

Tue, 2011-11-29 10:13

#2

cherry.anne

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Joined: 2011-11-28

Learning in Psychology (Changing behavior)

Changing a bad habit or behavior must always start within the person. It is called self-regulated learning. My professor in Psychology 140 (Principles of Learning) required us to memorize the process of the Generic Self-Regulation Model by Grant in class that’s why I still can recall it. I will share it with you so that if ever you feel the need to change any habit or behavior, you can use it. It starts with your issue or problem. You should personally know what your problem is or what behavior you need to change. Set goals after. Goals should be realistic and attainable. According to a psychology theory, there are three factors that can affect you: personal factors (either cognitive or biological), environment, and behavior. You need to identify the strongest factor that affects the behavior you want change. Or in simple term, the most effective strategy for you. Why? Because once you change that factor, eventually, your behavior will change too. Next thing that you must do is to act now, not later. Change your behavior little by little through the factor that you select. Monitoring comes after. See if you progress as time passes by. When you think you've already changed the behavior, evaluate the change. Then decide whether you’ll continue the strategy, change the strategy, or improve the strategy. Act again after. Just continue the cycle until you've completely changed the unwanted behavior.

Tue, 2011-12-13 18:01

#3

Emily Shearin

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Joined: 2011-12-01

Developmental Psychology: Pregnancy Stages

Pregnancy occurs during a time period of forty weeks that is ten lunar months or three trimesters. Each stage there is a different development from the fetus until finally the birth of a baby. What happens during those stages?

The first trimester is fourteen weeks long or three and a half lunar months. Fertilization happens at two weeks, but the first layer of skin does not appear until the week four. Shortly after during week five and six, the brain and heart start to develop. By week seven, before even the second lunar moon and only halfway through the first trimester the baby has the first detectable brain waves. Week eight is the marking end of the embryotic period it is also the beginning of the second lunar month. Finally, at week ten the basic brain structure is all set up, and by week twelve, there is a detectable heartbeat. The first trimester is over at week 14 and three and a half lunar moons with the sexual organs being visible.

The second trimester is weeks fifteen through twenty eight, which takes us to the beginning of the seventh lunar month. Fingers and toe prints are developed by week seventeen and at week twenty bone marrow starts to make blood cells. At week twenty for sensory brain waves begin to work and by the end of the second trimester, the brain convolutions begin.

The third and final trimester last from weeks twenty nine to week forty and through the tenth lunar month, and during this phase it is almost like the baby wakes up. Weeks thirty to week thirty there is a huge increase in brain growth, as well as the immune system starts at week thirty two as well. Around the week thirty five most heads start to move towards the pelvis. Finally, by forty weeks the baby is full term and ready to be born.

Fri, 2011-12-16 15:51

#4

Emily Shearin

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Understanding Reinforcement

Reinforcement in psychology means to reinforce, or strengthen, the probability or rate, of a specific behavior, as a response of the delivery of a specific stimulus. An example would be training a dog how to sit by giving it a treat, every time it follows the command sit properly. Eventually, the dog learns that when it follows the command properly, because it enjoys the treat. All together, there are four categories of reinforcement: negative, positive, punishment, and extinction. Here, I will explain what each is and give an example to help guide you.

Negative reinforcement is often confused with punishment, because of the word negative. However, it is the exact opposite. Negative reinforcement is when an aversive stimulus is taken away to increase a specific behavior or response. Imagine a husband being nagged by his wife to do the dishes, he even complains to his friends about it. One day he does the dishes and magically the nagging has stopped.

Positive reinforcement works by adding a stimulus that in enjoyable in order to increase a behavior or response. The example of the dog being trained to sit by giving it treats whenever it does the trick properly is positive reinforcement.

Punishment is adding in an aversive stimulus in order to decrease a behavior or response. The most known example is a child being spanked when they have done something wrong. The child will eventually associate the bad behavior with the aversive stimulus, and therefore, will stop the behavior or response to avoid the punishment.

Extinction is when something enjoyable is taken away to decrease or stop a certain behavior or response. A common example would be a teenager having their cell phone taken away because they stayed out too late. Much like punishment, the teenager will no longer stay out too late, because they want their cell phone.

Wed, 2011-12-21 21:40

#5

ViCairo

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Joined: 2011-12-19

Social Psychology: The Bystander Effect

The Bystander Effect is a social phenomenon, one where if you increase the number of individuals in a room, the less likelihoods of a chance for action to take place occur. Where in a room of 3 in comparison to being alone, if a fire were to start, there would be an increased chance for the person, who is alone in the room to report that fire, in comparison to the room of 3, where the percentile chance would lower. The reasoning behind this is possibly because of the 'oh someone else will report it' mentality, which is also a problem since a real-life example of it is a worldwide problem. You may have heard of the term when it comes to bullying when someone is getting bullied and there is a group of individuals who refuses to take action and stands around to watch the display of hostility thinking someone else will stop in and tell the aggressor to stop. This is also called the diffusion of responsibility that tends to occur in a large group of individuals, who do not feel the need to take action thinking someone else will do it. Another reason that no one reacts to the social situation is by example of a possible way to behave acceptably in social situations, if a group of people does nothing, people follow that example, so on so forth.

Thu, 2012-01-05 23:29

#6

emilyytlin

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Joined: 2011-12-31

Memory

Memory is the capacity for the encoding, storage, and retrieval of information. These determine whether or not a piece of information is remembered or forgotten. Encoding is the processing of information. Some kinds of information are encoded easier than others. On one hand, most people can remember what they had for lunch, even if they’re not trying to remember that. On another hand, most people cannot remember everything they’re reading in a textbook even if they’re trying to remember it. There are a few ways to encode information. Structural encoding is based on what the words look like. Phonemic encoding is based on what the words sound like. Semantic encoding is based on what the words mean, which requires a more thinking than structural or phonetic encoding, resulting in better memory. After entering the brain, information is stored. Using Richard Atkinson and Richard Shiffrin’s three-stage model, information is stored in three systems: sensory memory, short-term memory, and long-term memory. Sensory memory stores information in detail but for less than a second. Short-term memory stores information for about twenty seconds. Repeating can help short-term memory. Chunking small bits of information into larger pieces can also help short-term memory. Information can move to and from short-term memory to long-term memory. Long-term memory is nearly infinite and will stay forever, but it is not always retrievable. Retrieving memory can be easier given the associations, context, and mood.

Thu, 2012-01-05 23:29

#7

emilyytlin

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Types of Memory

Now, short-term memory is considered to be a working memory. It is not just for temporary information storage, but it is also an active system to be used when people process and examine things. Flashbulb memories are very detailed and associated with important events. For example, most people remember where they were when the World Trade Center was bombed. Implicit / Explicit Memory Implicit memory retains information unconsciously. For example, you may have gone to a hotel with your parents when you were five. Although you forgot your experience there, you know exactly where the swimming pool is. Explicit memory retains information consciously. This is needed to remember someone’s birthday. Declarative / Procedural Memory Declarative memory is the memory of factual information. Usually, declarative memory is explicit, because it involves conscious remembering. Learning U.S. History facts require declarative memory. Procedural memory is remembering how to do things, such as speaking a language, playing an instrument, or swimming. This is usually implicit, because people don’t consciously remember procedures. Semantic / Episodic Memory Semantic and episodic memories are two subsets of declarative memory. Semantic memory refers to general facts, while episodic memory refers to more personal facts. Remembering math equations are part of semantic memory. Remembering your best friend’s birthday requires episodic memory.

Thu, 2012-01-05 23:29

#8

emilyytlin

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Forgetting

Hermann Ebbinghaus was the first researcher to experiment on forgetting. He used himself as a test subject, memorizing lists of nonsense syllables and testing himself. He found that he forgot most of the syllables in a few hours, and he charted forgetting curves to graph how quickly he forgot over time. Later researchers found that meaningful information is retained more than nonsense syllables. There are ways to measure forgetting, by recall, recognition, and relearning. If you can remember without any external cues, you are recalling. In school, essay questions test recall since there is nothing to remind you except a blank page. Recognition is remembering with external cues. In school, multiple choice questions test recognition because the information is already on the page. It might take someone less time to relearn information. The time spent relearning divided by the time learning originally is the retention rate. We may forget for a variety of reasons. Sometimes, it is because of bad encoding. Encoding at a deeper level makes information harder to forget. According to the decay theory, memory fades over time, which explains why information is lost between sensory and short-term memory. Sometimes, memories can interfere with each other. Retroactive interference is when new information interferes with old information. Proactive interference is when old information interferes with new information. Sometimes, according to Freud, it is even better to forget because the truth is too painful.

Thu, 2012-01-05 23:30

#9

emilyytlin

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Joined: 2011-12-31

Remembering

Although there are so many ways to forget, there are also many ways to remember. Here are a few ways. Rehearsal. Practicing information can help people remember it. Overlearning. If you already know something, practice it more. This can help retain information. Distributed Practice. Learn the material little by little over a long period of time. This is more effective by cramming. Minimizing Interference. Sometimes, the information you learn can get in each other’s way. To minimize this interference, you can sleep after studying, since you cannot bring new material in while sleeping. Deep Processing. When learning material, think and pay attention. To process more deeply, you can use elaboration to associate the material being learned with previously learned material. Organizing. Organizing hierarchically, in categories, or in subcategories can be extremely helpful. For example, you can use an outline. Chunking material is also helpful, such as when people memorize social security numbers in smaller pieces. Mnemonics. You can use acronyms or rhymes to help remember concepts. Acronyms. These are words that are made from the first letters of other words. For example, ROY G. BIV can be used to remember the colors in the rainbow: red, orange, yellow, green, blue, indigo, and violet.

Thu, 2012-01-05 23:30

#10

emilyytlin

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Joined: 2011-12-31

More Methods of Remembering

Acrostics. These are sentences in which each word starts with the letter of the memory cue. For example, “Please Excuse My Dear Aunt Sally” can be used to remember the order of operations: parentheses, exponents, multiplication, division, addition, and subtraction. Narrative Methods. Make up a story to go along with a list of words. Rhymes. “I before E, except after C” is a common spelling rhyme. Visual Imagery. This xkcd comic uses this to remember the password, “correct horse battery staple.” Method of Loci. You can use this method by picturing yourself walking through somewhere familiar. Imagine each item you need remembered in a specific place as you walk along. When you need to recall the information again, walk through the same path, noting the items you saw. Link Method. Try associating items to be remembered with each other, such as with the xkcd comic. Peg Word Method. Remember a rhyme that associates numbers with words: one is a gun, two is a pew, three is a T, four is a floor, five is a dive, six is tricks, seven is heaven, eight is a crate, nine is a pine, and ten is a den. Visualize each item to be associated with the following objects. When the list needs to be recalled, you will first see the gun and then remember what it is associated with, and so on for each item on the list.

Tue, 2012-01-17 13:58

#11

emilyytlin

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Psychological Research

Since psychology is a science, it requires testable methods in research. The goals of research are to figure out how to describe behavior, to discover the conditions in which events occur, and to apply their knowledge in real-world problems. The following concepts are included in psychological research. Variables – the characteristics, behaviors, or conditions that are being measured. Subject – the animal or human being studied. Sample – a collection of subjects that are being studied. Population – all the people or animals that are represented in a sample. This is too big to be measured, so psychologists take a sample. The scientific method standardizes psychological research. Under the scientific method, psychologists must form a hypothesis, test it, and then form a theory to organize their information. A scientific theory is generated after collecting a lot of evidence. This is different from a theory in the colloquial speak, in which theories do not need much evidence at all. A good scientific theory is replicable, falsifiable, precise, and parsimonious. Replicable means that others can repeat it can get the same thing. Falsifiable means that others can prove it wrong. Precise means that research should have operational definitions that can define the variables studied. Parsimonious means that researchers should apply the simplest possible explanation to their observations.

Tue, 2012-01-17 13:58

#12

emilyytlin

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Correlational Research Methods

Some research methods are correlational, such as case studies, surveys, natural observation, and laboratory observation. However, correlation is not the same as causation. Two things can be related without one of them causing the other to happen. For example, ice cream sales are correlated with shark attacks. Neither of them causes each other; they’re just the byproducts of summertime. Correlation can be measured by a correlation coefficient between -1 and +1. A positive correlation means that both variables increase. A negative correlation means that one variable increases while another decreases. There is more correlation near +1 and -1, and a correlation of 0 means that there is no relationship between them. Case Study In a case study, a subject is studied in depth through interviews, observation, and testing. With only one subject, this can be quite biased. Survey People are given questionnaires or are interviewed. This is self-reported data, which can be problematic because subjects can lie, be confused, or forget things. Naturalistic Observation Researchers observe people without intruding. Laboratory Observation Researchers observe people controlling the environment and use equipment. Psychological Tests Tests are standardized to collect information about personality, emotions, aptitudes, interests, or abilities. These are compared to the standard level of performance.

Tue, 2012-01-17 13:59

#13

emilyytlin

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Causational Research Methods

Experiments can yield information about cause/effect relationships. Researchers change the independent variable in an experiment and observe how it changes in the dependent variable. These groups are divided in the experimental and control groups. Both groups receive the same treatment, except the independent variable is manipulated in the experimental group. By doing so, researchers can compare the experimental group to the control. Researchers assign people to these groups randomly so that all subjects have an equal chance of being in either group. There are biases in experiments. When the sample studied in an experiment does not represent the population, sampling bias occurs. When the subjects’ expectations change their behavior, subject bias occurs. This include the placebo effect, in which subjects think they are given the real drug when they are not, and the social desirability bias, in which subjects describe themselves to make themselves sound better. When the researchers’ expectations change their research, experimenter bias occurs. To reduce bias, a double-blind procedure is used so that the researcher and the subject both don’t know who’s coming from the experimental group or the control group. A test is reliable if it yields the same result when replicated. A test is valid if it measures what it is supposed to measure. Be sure not to confuse them.

Tue, 2012-01-17 13:59

#14

emilyytlin

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Ethics in Psychology

Ethics is the code people use to determine right and wrong. Many unethical experiments were done for science. During the Holocaust, Nazi doctors performed all sorts of experiments on the inmates in concentration camps. One involved testing what temperature the human body freezes, measuring the temperature of the human body when it dies. What we currently know about the effects of freezing on the human body is based on the results of this experiment. This is an ethical problem. The American Psychological Association requires its members to abide by its code of ethics. For Human Subjects Researchers must protect subjects from harm, allow them to withdraw at any time, and protect their anonymity. They must also give their subjects informed consent telling them what happens during the experiment, and the subject must agree voluntarily. Sometimes researchers must deceive subjects to perform tests because people behave differently under observation. Deception is only ethical if the study will provide information, if it is impossible to do without deception, and the subjects are debriefed afterwards. For Animal Subjects Research on animal subjects can help us learn about animals, find ways to improve human welfare, and study things that cannot be studied on human subjects. Some people are against animal research because they think animals should have the same rights as humans.

Tue, 2012-01-17 14:00

#15

emilyytlin

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Interpret Data in Psychology

Psychologists can end up with a lot of data, and to interpret this data, they use statistics. They might use histograms or bar graphs to see how their data is distributed. Putting data in a chart or graph makes it easy to see results and trends in data. Psychologists summarize their data with measures of central tendency: mean, median, and mode. The mean is the arithmetic average of the scores. The median is the middle score. The mode is the most common score. Sometimes, the distribution can be skewed with a few people scoring very high or very low. If there are a few extremely high scores, it is positively skewed. If there are a few extremely low scores, it is negatively skewed. To measure variation in data, psychologists use the range and standard deviation. The range is the highest score minus the lowest score. The standard deviation is the how much the data varies around the mean. After analyzing their data, psychologists determine how statistically significant their data is. Their data must be large and varied to be representative of the population and not have much variation in scores. The result is statistically significant if it occurs by chance less than once ever twenty times. This is p <= .05.

Tue, 2012-01-17 14:00

#16

emilyytlin

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Behavioral Genetics

Behavioral genetics is a branch of psychology focusing on the genetic reason why people behave differently. It is based on a few basic genetic concepts. Each cell has 46 chromosomes, in 23 pairs, except for sex cells. Sex cells have 23 chromosomes. Chromosomes are made up of DNA, containing thousands of genes. Genes are segments of DNA. DNA is made up of nucleotides, named C, A, T, and G. Genes are transformed into proteins, like enzymes or hormones. People share 100% of genes with an identical twin, 50% with a parent, sibling, or nonidentical twin, and 25% with a grandparent. Monogenic traits are controlled by a single gene. Polygenic traits are controlled by several genes. Most traits are polygenic, such as intelligence. Usually, a particular psychological trait can vary significantly, such as intelligence. These differences can be due to genes or the environment, so psychologists use heritability to estimate how much of a trait’s variation is due to genes. However, heritability does not determine how much genes influence psychological traits, only how much differences can be attributed to genes. Heritability is higher among people in the same environment. No matter how heritable psychological trait is, it is still influenced by the environment.

Tue, 2012-01-17 14:01

#17

emilyytlin

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Genetic Studies

Family Studies Researchers look for similarities in a psychological trait amongst family members. If a trait is heritable, then it should be similar between relatives, and the closer the blood relation, the more similar it should be. However, family studies cannot prove that a trait is genetically inherited because families usually also share the same environment. Twin Studies Twin studies give psychologists more evidence whether or not a trait is inherited or not. In these studies, psychologists compare identical twins to fraternal twins, assuming that the twin pairs are raised in the same environment. This means when a trait is more similar between identical twins than between fraternal twins, this comes from more shared genes instead of the environment. However, identical twins may not be raised in the same environment. Separated Twin Studies To avoid environmental factors, researchers sometimes study twins separated from birth and brought up in different families. When these twins share a trait, it is usually due to genes. However, separated twins may in fact share much of their environments since they were in the same environment before they were born, adoption agencies place twins in similar households, and people might treat them similarly because they look the same.

Tue, 2012-01-17 14:01

#18

emilyytlin

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More Genetic Studies

Experiences and Behavior Since environmental stimuli can form neural connections, experiences can affect behavior. Research shows that babies with consistent and loving contact with a caregiver achieve optimal brain development. Neglected babies experience emotions that determine their brain development. In the same way, soldiers in wars can suffer brain damage from being in a stressful environment, even without physical injury. Adoption Studies Researchers can compare children’s biological parents to their adoptive parents. These children have their biological parents’ genes, but their adoptive parents’ environment. If a trait of adoptive children is more similar to that of their biological parents, then this trait is heritable. With all of these experiments, psychologists have determined that genes do influence psychology, but environmental factors such as prenatal environment, parental influence, nutrition, experiences, peer pressure, and culture norms all are important too. Culture norms are the societal expectations we follow. Both genetics and environmental factors interact together. Sometimes, people are predisposed for a particular psychological trait, and their environment they live in shapes that trait. Sometimes, their psychological traits can even shape their environments.

Tue, 2012-01-17 14:01

#19

emilyytlin

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Evolution

In evolutionary psychology, psychologists use evolution to explain behaviors. Evolution is the change of genes in the population over a long amount of time. Evolutionary psychologists study how natural selection causes patterns of behavior. Charles Darwin’s theory of natural selection says that certain characteristics are advantageous for survival or reproduction. These characteristics would be passed down more frequently than other traits. A trait with reproductive advantage helps it mate successfully to pass on its genes. A trait with survival advantage helps it live so that it can mate and pass on its genes. W. D. Hamilton came up with the concept of inclusive fitness. Inclusive fitness is the reproductive fitness of an organism as well as the effect it has on increasing reproductive fitness in other organisms. This explains why organisms sacrifice themselves to save more people in their species. An inherited characteristic that becomes predominant in a species because it is advantageous is an adaption. Since evolution takes a long time, this adaptation can still persist in organisms even after it is useful. Evolution is based on mutations, or tiny changes in genes. Mutations occur in the formation of sperm or egg cells because of an error in copying the DNA or because of random arrangement of DNA. Mutation can result in a new trait, and if this new trait is advantageous, then the mutated gene will be passed on more frequently than other traits.

Tue, 2012-01-17 14:02

#20

emilyytlin

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Evolutionary Psychology

Evolutionary psychologists use evolutionary theory to explain psychological traits. Since physical characteristics have evolved, patterns of behavior can evolve, too. Adaptive behaviors that increase reproductive success are passed on from generations because of natural selection. Mating behavior is a huge part of reproductive success. Robert Trivers says that mating strategies depend on the parental investment made by males and females in a species. In most species, males and females do not make the same parental investments. The sex that invests more discriminates when finding a mate and the sex that invests less competes with its own sex to find a mate. Generally, the female makes the bigger parental investment. These females would choose mates based on some characteristics. For example, a female peacock would choose a mate based on how colorful their tail feathers are. This process is sexual selection, which makes organisms more likely to mate. Adaptations that are the result of sexual selection are not always helpful, such as the colorful tail feathers. Polygyny is when one male mates with many females. Polygyny occurs in species in which males invest in parenting than females. Females can then pick the winners in the competitions, which ensure that their offspring would have good genes.

Tue, 2012-01-17 14:03

#21

emilyytlin

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Problems with Evolutionary Psychology

Evolutionary psychologists use the parental involvement theory to explain human behaviors, too, since women are more likely to be monogamous, and men are more likely to be promiscuous. Other scientists say that these explanations are not applicable to humans because these theories are derived from stereotypes. The way humans behave is complex, and their culture influences behavior. Also, it is difficult to relate variation in behavior to reproductive success. Evolutionary psychologists can also use their theories to put forth their own political agendas, which is not ideal. Some scientists do not approve of evolutionary psychology because they work backwards from an observation to develop their own theories. Just because a trait exists does not mean that it is adaptive. This trait might have been helpful before but is not helpful now, or it was a result of other adaptive traits. Evolutionary psychologists once did a study on sex differences in color preferences. The results showed that females liked red colors more and that they are better at differentiating colors than males. Evolutionary psychologists say that this is because women used to pick berries to eat and needed to differentiate colors to not be poisoned, their color differentiation adapted. However, women’s color preferences may just be the effect of different gender socialization.

Tue, 2012-01-17 14:03

#22

emilyytlin

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Central Nervous System.

The nervous system is a complex network of nerves that communicate using electrical chemical signals. It receives and processes all the information in the body, and it has two main branches, the central nervous system and the peripheral nervous system. Central Nervous System The central nervous system receives information from the senses and processes it. It contains the brain and the spinal cord. These are immersed in cerebrospinal fluid, cushioning and nourishing the brain. The cerebrospinal fluid is protected by the blood-brain barrier, which blocks drugs and toxins. This membrane lets some substances in and keeps others out. The spinal cord connects the brain to the body, running all the way down the back. The spinal cord controls spinal reflexes, or the automatic reflexes that do not need the brain, and it sends messages from the brain to other parts of the body and back. The bones in the spine protect the spinal cord because even minor injuries to the spinal cord can cause loss of feeling in certain body parts, loss of muscle control, loss of organ function, and even paralysis. Spinal cord injuries are usually permanent, but stem cell research is now hoping to change that. The brain is the most important part of the central nervous system. It processes information from the senses, contains memories, dreams, ideas, and more.

Tue, 2012-01-17 14:03

#23

emilyytlin

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Peripheral Nervous System.

The parts of the nervous system that are not the brain and the spinal cord are a part of the peripheral nervous system. The peripheral nervous system is made up of the somatic nervous system and the automatic nervous system. Somatic Nervous System The somatic nervous system contains nerves that connect the central nervous system to the skeletal muscles that help us move and sense organs. This controls voluntary actions. These nerves can be afferent or efferent. Afferent nerves carry information from the muscles and senses to the brain and spinal cord, and efferent nerves carry information from the brain and spinal cord to the muscles and senses. Autonomic Nervous System The autonomic nervous system contains nerves that connect the central nervous system to the other muscles in the glands, heart, blood vessels, and smooth muscles. Smooth muscles are involuntary muscles that help the bladder and stomach do their jobs. The autonomic nervous system controls the involuntary actions in the body, such as breathing, heartbeat, digesting, and sweating, and it is divided in the sympathetic and parasympathetic nervous systems. The sympathetic nervous system makes the body ready for emergencies, such as the fight-or-flight reaction. In case of a challenge, the sympathetic nervous system would slow down digestion, draw blood away from the skin to the skeletal muscles, and release hormones for quick reactions. The parasympathetic nervous system is active in rest, helping the body store energy, slowing heartbeat, decreasing blood pressure, promoting digestion.

Tue, 2012-01-17 14:04

#24

emilyytlin

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Introduction to Neurons

The nervous system has two kinds of cells: neurons and glial cells. Glial cells support the whole nervous system, giving neurons structural support, insulating and nourishing neurons, and removing waste products. The neurons, on the other hand, send and receive information along the nervous system. Neurons all have the same structure. Each neuron has a cell body, called a soma, in the center, containing the nucleus and other structures in cells. Neurons also have branches sticking out of them, called dendritic trees. An individual branch is a dentrite, which receive information. The axon is the long fiber that runs inside the neuron, which sends information. Some axons have a myelin sheath, coating the axon, protecting myelin. The myelin sheath makes nerve impulses travel faster in the neuron. This is important because diseases can damage the myelin sheath. One such disease is polio, paralyzing the body. Another such disease is multiple sclerosis, making it difficult for people to control the muscles. At the end of the axon are terminal buttons. These buttons release neurotransmitters, chemicals that can jump to other neurons and activate them. The space between the axon of a neuron and the cell body of another neuron is a synapse.

Tue, 2012-01-17 14:05

#25

emilyytlin

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Neuron Communications

Alan Hodgkin and Andrew Huxley discovered very important ways neurons transmit information in 1952. Testing the large axons of giant squid and putting electrodes in the axons, Huxley and Hodgkin discovered that nerves rely on electrochemical reactions. Nerves exist to transmit electrochemical signals. There are fluids inside and outside neurons. The fluid contains positively charged and negatively charged ions. Sodium and potassium ions are positive, and chloride ions are negative. A neuron in the resting state is inactive, so it is more negatively charged than the outside. This provides potential energy to the neuron as the resting potential. This resting potential is about 70 mV. When neurons are stimulated, the cell membrane opens up, letting in positive ions. This is called the action potential. The action potential can flow quickly through an axon. Then channels in the membrane close so that no more positive ions can enter. It is closed for a while, and the neuron can’t send impulses. The time the membrane is closed is the absolute refractory period, about 1-2 ms. Neural impulses are all or nothing. Either a neuron fires or it does not. The strength of the impulses is all the same. After a stimulus reaches a designated threshold, the neuron sends an impulse, and if it does not reach the threshold, the neuron does not send an impulse. Weak stimuli do not mean weak impulses.

Tue, 2012-01-17 14:05

#26

emilyytlin

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Synapse

The gap between the two neurons in a synapse is the synaptic cleft. The cell that sends the signal is the presynaptic neuron, and the cell that is receiving the signal is the postsynaptic neuron. The chemicals that allow neurons to communicate are called neurotransmitters. The neurotransmitters are contained in synaptic vesicles, or small sacs in the terminal buttons. When the action potential gets to the terminal buttons at the end of the axons, the synaptic vesicles with their neurotransmitters combine with the presynaptic cell membrane. This way, the neurotransmitters fill up the synaptic cleft. After the neurotransmitters get to the postsynaptic cells, they attach to the corresponding receptor sites. Neurotransmitters attract only to certain receptors just as keys only open certain locks. When neurotransmitters link to the receptor, the receptor changes its voltage. This is called the postsynaptic potential (PSP). These PSPs can be excitatory or inhibitory. When the neurotransmitter binds to an excitatory receptor, there is a positive change in voltage, which is the excitatory PSP. This makes it more likely that there would be an action potential in the postsynaptic cell. When the neurotransmitter binds to an inhibitory receptor, there is a negative change in voltage, which is the inhibitory PSP. This makes it less likely that there would be an action potential in the postsynaptic cell.

Tue, 2012-01-17 14:06

#27

emilyytlin

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Joined: 2011-12-31

Neurotransmitters

So far, scientists have discovered around twenty different neurotransmitters, and new ones are being discovered every day. The nervous system can communicate because of all the different kinds of neurotransmitters, and different neurotransmitters can do different things. Acetylcholine controls muscle movement, attention, memory, and emotion. People with Alzheimer’s disease have too little of this. Dopamine controls voluntary movement, learning, memory, and emotion. People with schizophrenia have too much of this, and people with Parkinson’s have too little of it. Serotonin controls mood, sleep, aggression, temperature regulation, and pain suppression. People with depression have too little of it. Endorphin controls pleasure and pain relief. Norepinephrine controls dreaming, memory, emotion, learning, heart rate, and the digestive process. People with depression have too little of it. GABA is the primary inhibitory neurotransmitter. Glutamate is the primary excitatory neurotransmitter. Chemicals that copy a neurotransmitter are called agonists. They also bind to receptors and generate postsynaptic potentials. Nicotine is an agonist for acetylcholine, copying it. It competes for acetylcholine receptors, making the nerves highly stimulated, which makes the body feel alert and elated. Chemicals that block a neurotransmitter are called antagonists. These bind to receptors and do not generate postsynaptic potentials. When they bind to receptors, they stop the neurotransmitters from doing so. Curare is an antagonist for acetylcholine. It causes paralysis. When it binds to acetylcholine receptors, the real acetylcholine cannot communicate between the neurons and the muscles. Doctors use curare to paralyze patients during surgery, and South American natives used it as arrow poison.

Tue, 2012-01-17 14:06

#28

emilyytlin

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Joined: 2011-12-31

Study the Brain

To study the brain, scientists cannot use cadavers; instead, they have to use a living brain. Invasive studies in which scientists put equipment in the brain can only be done in humans sometimes during necessary brain surgery. This means that scientists use invasive techniques more in animal studies. These include lesioning studies, in which an electrode and electric current burn a small part of the brain, and electric stimulation of the brain, in which an electrode sends a weak electric current to activate a structure in the brain. To research the human brain, researchers usually cannot use invasive techniques, but they can use electroencephalographs (EEGs), which are electrodes on the scalp that can record electrical activity in the brain. Now, there are high tech devices that can be used to study the brain. In computerized tomography (CT), x-rays are taken of the brain at different angles. When the x-rays are combined, a computer can make a picture of the brain. In magnetic resonance imaging (MRI), the brain structure and function can be seen. MRI consists of magnetic fields and radio waves, and a computer can enhance these pictures. In positron emission tomography (PET) scans, scientists inject subjects with a radioactive chemical that collects where the brain is active. When scientists look at the radioactivity in the brain with a scanner and computer, they can find which parts of the brain are active in certain tasks.

Tue, 2012-01-17 14:06

#29

emilyytlin

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Joined: 2011-12-31

Forebrain

The forebrain is the biggest part of the brain, containing the thalamus, the hypothalamus, the limbic system, and the cerebrum. The thalamus is the pathway for sensory information, except smell. The hypothalamus is under the thalamus, controlling the pituitary gland, autonomic nervous system, regulating body temperature, and drives for hunger, thirst, and sex. The limbic system has the hippocampus, the amygdala, and the septum. There are also some parts of the limbic system in the thalamus and hypothalamus. The limbic system processes emotions, the amygdala controls aggression and fear, and the hippocampus controls memory. The cerebrum is the biggest part of the brain, controlling the most complex processes like abstract thought and learning. The outer layer is wrinkled and is the cerebral cortex. The corpus callosum is a system of fibers that run along the cerebrum, dividing the cerebrum into two hemispheres. Each hemisphere has four lobes. The occipital lobe has the primary visual cortex, controlling visual information. The parietal lobe senses body position and contains the primary somatosensory cortex, which handles touch information. The temporal love contains Wernicke’s area, which handles language comprehension, and the primary auditory cortex, which processes auditory information. The frontal lobe contains the primary motor cortex, which controls the muscles, and it also controls memory, planning, creativity, decision making, and social skills. The left frontal lobe contains the Broca’s area, which handles speech making.

Tue, 2012-01-17 14:07

#30

emilyytlin

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Joined: 2011-12-31

Midbrain, Hindbrain, Lateralization

The hindbrain contains the medulla, the pons, and the cerebellum. The medulla is next to the spinal cord, and it controls unconscious functions like breathing. The pons control sleep and dreams. The cerebellum controls balance and motor skills. The midbrain helps us locate places and contains neurons that release dopamine. The reticular formation is also in the midbrain, which controls sleep, pain perception, breathing, and reflexes. Since the left and right hemispheres of the brain do different things, the brain is lateralized. The left hemisphere controls verbal processing tasks like reading, while the right hemisphere controls nonverbal processing tasks such as drawing. Roger Sperry and Michael Gazzaniga conducted research in lateralization using those who went through split-brain surgery. People with epileptic seizures sometimes have their corpus callosum cut so that their brain hemispheres are separated. The nervous system is set up so that the left hemisphere of the brain controls the right side of the body and the right hemisphere of the brain controls the left side of the body. Vision and hearing are slightly different in that their information go to the entire brain, but they still register with the opposite hemisphere first. Because of the corpus callosum connecting the hemispheres, the brain’s hemispheres’ communication with the opposite sides of the body does not affect everyday life usually.

Tue, 2012-01-17 14:08

#31

emilyytlin

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Joined: 2011-12-31

Endocrine System

The endocrine system is made up of glands that secrete hormones, which are chemicals that regulate functions in the body. These hormones are secreted into the bloodstream, and then the hormones travel to where they need to go. Though hormones are slower than neurotransmitters, hormones last longer. The pituitary gland is next to the hypothalamus of the brain, and it is the main gland of the endocrine system. The hypothalamus can stimulate the pituitary gland and make it release hormones to control other glands. Here are some of the most well-known hormones and their functions. Thyroxine is produced by the thyroid gland, and it regulates the metabolic rate. Insulin is produced by the pancreas, and it regulates blood sugar levels. Melatonin is produced by the pineal gland, and it regulates biological rhythms and sleep. Cortisol, Norepinphrien, Epinephrine, and Adrenaline are produced by the adrenal gland, and they regulate body functions in stressful situations. Androgen is produced by the testes and it regulates male secondary sex characteristics and sexual arousal. Estrogen is produced by ovaries, and it regulates female secondary sex characteristics and menarche. Progesterone is produced by ovaries, and it prepares the uterus for the planting of the fertilized eggs.

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