Week 2 Intro to Psych
Week 2 Intro to Psych 100
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This 22 page Class Notes was uploaded by Sophomore Notetaker on Saturday October 1, 2016. The Class Notes belongs to 100 at Washington University in St. Louis taught by Rice, Duchek, Carpenter in Fall 2016. Since its upload, it has received 5 views. For similar materials see Intro to Psychology in Psychology at Washington University in St. Louis.
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Date Created: 10/01/16
3.1 How Does the Nervous System Operate? Neurons – the basic units of the nervous system Cells that receive, integrate, and transmit information in the nervous system They operate through electrical impulses, communicate with other neurons through chemical signals, and form neural networks The Nervous System Has 2 Basic Divisions Central Nervous System (CNS) – brain and spinal cord Peripheral Nervous System (PNS) – all the other nerve cells in the rest of the body that are not CNS o Includes somatic and autonomic systems The CNS and PNS are anatomically separate, but functions are interdependent PNS sends a variety of information to the CNS CNS organizes and evaluates that information and then directs the PNS to perform specific behaviors or make bodily adjustments Neurons Are Specialized for Communication Neurons are specialized for communication o Excitable – powered by electrical impulses and communicate with other nerve cells through chemical signals Neuron Phases o Reception – neurons take in the chemical signals from neighboring neurons o Integration – incoming signals are assessed o Transmission – pass their own signals to other receiving neurons Type of Neurons o Sensory Neurons – detect information from the physical world and pass that information along to the brain, usually through the spinal cord Somatosensory neurons – provide information from the skin and muscles o Interneurons – communicate with local or short-distance circuits Integrate neural activity within a single area rather than transmitting info to other brain structures or body organs o Motor Neurons – direct muscles to contract/relax, producing movement o Sensory and motor neurons work together to control movement o Sensory receptors in skin sensory neurons interneuron motor neuronmuscle contraction -if touch something pointy Neuron Structure o Dendrite – short, branchlike, appendages that detect chemical signals from neighboring neurons o Cell body – where information from thousands of other neurons is collected and integrated o Axon – long narrow outgrowth of a neuron by which info is transmitted to other neurons Vary in length Nerve – bundle of axons that carry away info between the brain and other parts of the body o Terminal buttons – at the ends of the axons; small nodules that release chemical signals from the neuron into the synapse o Synapse – site where chemical communication occurs between neurons Neurons communicate by sending chemicals into synapse – a tiny gap between the axon of the “sending” neurons and the dendrites of the “receiving” neurons Chemicals leave 1 neuron, cross the synapse, and pass signals along to the other neuron’s dendrites o Messages are received by the dendrites processed in the cell body transmitted along the axon sent to other neurons via chemical substances released from the terminal buttons across the synapse. o A neuron is covered by a semipermeable membrane, a fatty barrier that does not dissolve in the watery environment inside and outside the neuron Membrane has ion channels – allows ions to pass in/out of cell when the neuron transmits signals down axon By controlling movement of ions, membrane plays an important role in communication between neurons; it regulates concentration of electrically charged molecules that are basis of neuron’s electrical activity The Resting Membrane Potential Resting membrane potential – the electrical charge of a neuron when it is not active o Electrical charge inside and outside the membrane is different; this is because the ratio of (-) and (+) ions is greater inside the neuron than outside it o It is more (-) inside the neuron than outside (-70 mV) = polarized o The polarized neuron (at rest) creates electrical energy necessary to power firing of neuron Roles of Na+ and K+ o Each channel matches a specific type of ion: Na+ channels allow Na+ but not K+ (same for K+ channels) o The flow of ions through each channel is controlled by a gating mechanism When the gate is open, ions flow in/out; closed gate prevents this o Ion flow is affected by cell membrane’s selective permeability; b/c of this, more K+ is inside the neuron than Na+ Na+ and K+ Pump: increases K+ and decreases Na+ inside the neuron o Helps maintain resting membrane potential o Contributes to polarization Action Potentials Cause Neural Communication Action potential (neural firing) – the electrical signal that passes along the axon o The signal causes the terminal buttons to release chemicals that transmit signals to other neurons o Signals arrive at dendrites by the thousands; 2 types of signals: Excitatory – depolarize the cell membrane (decrease polarization by decreasing (-) charge inside the cell) – make it more (+) Increases the likelihood that neuron will fire Inhibitory – hyperpolarize cell (increase polarization by increasing (-) charge inside the cell) – make it more (-) Decreases the likelihood that neuron will fire Excitatory and inhibitory signals received by dendrites are combined with the neuron It total amount of excitatory input surpasses neurons firing threshold (-55 mV), an action potential is generated When a neuron fires, the Na+ gate in the cell membrane opens allows Na+ to rush into neuron causes the inside of the neuron to become more (+) than outside K+ channels open up to allow K+ inside the cell to rush out The change from (-) (+) inside the neuron is the basis for an action potential As Na+ channels close, Na+ stop entering the cell (same for K+ channels) o The electrical charge inside the cell starts out slightly (-) in initial resting state o As cell fires and allows more (+) ions inside, charge becomes (+) o Through natural restoration, charge returns to slightly (-) resting state Na+ channels open (-) K+ channels open (gets more positive; K+ rushes out) depolarization (makes it more positive) Na+ channels close repolarization (gets more negative) K+ channels start to close (-) When neurons fire, the cell membrane’s depolarization moves along axon like a wave; Na+ channels open in a series; action potentials always move down the axon away from the cell body terminal buttons Electrical signals travel quickly down the axon because of fatty myelin sheath myelin sheath – encases and insulates the many axons o made up of glial cells; sheath grows along on axon in short segments; between these segments are nodes of Ranvier – small gaps of exposed axon o action potential skips along axon; pauses briefly to be recharged at each node along the axon o for axons without myelin, Na+ channels along each part of the membrane must open (speed decreased) loss of myelin sheath means that visual information is disrupted and motor actins become jerky and uncoordinated All-or-None Principle – dictates that a neuron fires with the same potency each time; it does not fire in a way that can be described as weak/strong o How the neuron fires: the stronger the stimulation, the more frequently it fires action potentials Neurotransmitters Bind to Receptors Across the Synapse Presynaptic neuron – the neuron that sends the signal Postsynaptic neuron – the neuron that receives the signal How Neurotransmitters Work o Inside each terminal button are neurotransmitters – chemicals that are made in the axon and stored in vesicles; transmit signals from 1 neuron to another When released by the vesicles, the neurotransmitters convey signals across the synapse post synaptic cells o After the action potential travels to terminal buttons, it causes the vesicles to attach to the presynaptic membrane and release their neurotransmitters into synapse o Neurotransmitters then travel across the synapse and bind to receptors on postsynaptic neuron Receptors – specialized protein molecules on the postsynaptic membrane o Binding of neurotransmitters and receptors causes ion channels to open/close more tightly, producing an excitatory/inhibitory signal in postsynaptic neuron Neurotransmitters are made in the axon they are stored in vesicles action potentials cause vesicles to fuse to the presynaptic membrane and release their contents into the synapse neurotransmission is terminated by reuptake, enzyme deactivation or autoreception released neurotransmitters bind to postsynaptic receptors Neurotransmitters also block new signals until its influence is terminated 3 major events that terminate its influence: o Reuptake – when the neurotransmitter is taken back into the presynaptic terminal buttons; an action potential prompts terminal buttons to release the neurotransmitter into the synapse and then take it back for recycling Cycle of reuptake and release repeats continuously o Enzyme deactivation – when an enzyme destroys the neurotransmitter in synapse; different enzymes break down different neurotransmitters o Autoreception – autoreceptors monitor how much neurotransmitter has been released into the synapse; when excess is detected, the autoreceptors signal the presynaptic neuron to stop releasing the neurotransmitter Receptor has specific response (excitatory/inhibitory); same neurotransmitter can send excitatory/inhibitory postsynaptic signals Neurotransmitters can produce different effects, depending on properties of the receptor and receptors location in the brain Neurotransmitters Influence Mental Activity and Behavior Agonists – drugs and toxins that enhance the actions of neurotransmitters o Increase how much neurotransmitter is made o Block the reuptake of neurotransmitters o Mimic a neurotransmitter activating/increasing its effects Antagonists – drugs and toxins that inhibit these actions o Decrease the release of neurotransmitters o Destroy neurotransmitters in synapse o Mimic a neuro. blocking neurotransmitter binding Drugs and toxins can minimize neurotransmitter and bind with their receptors as if they were the real thing; the receptor/lock can’t tell if neurotransmitter/key from a forgery and activate it Types of Neurotransmitters o Acetylcholine (Ach) – responsible for motor control at junctions between nerves and muscles After moving across synapses, Ach binds with receptors on muscle cells, making the muscles contract/relax Ex: Ach excites skeletal muscles and inhibits heart muscles Involved in complex mental processes: learning, memory, sleeping and dreaming Because it affects memory and attention, drugs that are Ach antagonists can cause temporary amnesia Alzheimer’s associated with diminished Ach functioning o Monoamines – same basic molecular structure; regulate arousal, regulate feelings and motivate behavior Epinephrine – (adrenaline) a burst of energy caused by a release of it that binds receptors throughout the body; helps prepare body for dealing with threats Norepinephrine – states of arousal and alertness; useful for clarity of attention Serotonin – important for emotional states, impulses control and dreaming Low levels = sad/anxious moods, food cravings, aggressive behavior Some drugs block serotonin reuptake and leave more serotonin at synapse to bind with postsynaptic neurons; treat mental disorders Selective Serotonin Reuptake Inhibitors (SSRIs) – treat depression Dopamine – motivation and reward; communicates which activities may be rewarding Activates us to eat, have sex, drink when thirsty Also involved in motor control and planning; helps guide behavior toward things –objects and experiences – that will lead to additional reward Lack of dopamine – problems with movement o Parkinson’s disease – neurological disorder marked by muscular rigidity, tremors, difficulty with voluntary action; dopamine- producing neurons slowly die off; people alter on suffer from cognitive and mood disturbances Injecting with L-DOPA, helps surviving neurons produce more dopamine; only temporarily Deep brain stimulation – involves surgically implanting electrodes deep within brain and then using mild electrical stimulation in regions affected by disorder; reverse many of movement problems associated o Successful, for as long as 11 years; helps with motor symptoms, but other symptoms get worse over time o GABA – primary inhibitory neurotransmitter in the nervous system; more widely distributed throughout brain than other neurotransmitters Without inhibitory effect of GABA, synaptic excitation might get out of control and spread through brain chaotically Epileptic seizures caused by low GABA levels GABA agonists – used to treat anxiety disorders o Glutamate – primary excitatory neurotransmitter in nervous system; involved in fast acting neural transmission throughout brain Glutamate rectors aid learning and memory by strengthening synaptic connections Excessive glutamate release overexcitement of brain seizures Linked to diseases, brain damage o Endorphins – natural pain reduction and reward; body’s natural defense against pain Pain is useful because it alerts of danger but also interferes with adaptive functioning; endorphins painkilling effects help animals perform behaviors even when they are in pain Morphine – bind with endorphin receptors reducing experience of pain Alters way pain is experienced rather than blocking nerves that transmit pain signals 3.2 Brain Structures and Functions Early Researchers on Brain Franz Gall hypothesized about effect of mental activity on brain anatomy; proposed that if a person used a particular mental function more than another, then that part of brain would grow and produce a bump in skull o By feeling the skull, one could describe personality of individual – phrenology o Not much scientific facts but spread principle that brain functions were localized Broca – one of his patients lost ability to say anything other than word ‘tan’, though he could still understand the language; looked at brain and found large area of damage in section of front left side led to conclude this region was important for speech Broca’s Area – left frontal region, crucial for production of language Scientists Can Watch the Working Brain Physiological assessment – measurements of bodily systems o Ex: blood pressure, breathing rate, perspiration rate o Examine how bodily functions change in association with behaviors/mental states Polygraphs – lie detector; people who are lying, experience more arousal and stress Electrophysiology – data collection method that measures electrical activity in the brain; small electrodes on scalp pick up brain’s electrical activity o Electroencephalograph (EEG) – device that measures brain activity; useful because different behavioral states produce different and predictable EEG patterns Limited because records all brain activity, too “noisy” or imprecise to isolate specific responses to particular stimuli o Event-related potential (ERP) – conducting many trials with a single individual and averaging across the trials to see how brain activity changes in responses to specific stimuli Brain Imaging – methods measure changes in rate of the flow of blood to different regions in brain; can monitor which brain areas are active when people do certain tasks or experience a certain event o Positron Emission Tomography (PET) – a method of brain imaging that assesses metabolic activity by using a radioactive substance injected into the bloodstream To find most active brain areas Increased blood flow carrying the radioactive material leads these regions to emit more radiation Downside- need to inject radioactive substancelimit use of PET o Magnetic Resonance Imaging (MRI) – a powerful magnetic field is used to momentarily disrupt the brain’s magnetic forces Energy is released from brain tissue in a form that can be measured by detectors surrounding the head Researchers can produce a high-resolution image of brain b/c different types of brain tissue release energy differently Valuable for providing information about structure of brain; can determine location of brain damage/trauma o Functional Magnetic Resonance Imaging (fMRI) – make use of brain’s blood flow to map the working brain Measures blood flow indirectly by assessing changes in blood oxygen level Participant performs a task that differs from the 1 in only 1 way and that reflects the particular mental function of interest; researchers then compare images to examine differences in blood flow (brain activity) o Limitations of Brain Imaging use TMS then Findings are correlational Know that certain brain regions are active when task is being performed Do not know whether each brain region is necessary for that particular task Transcranial Magnetic Stimulation (TMS) – uses a very fast but powerful magnetic field to disrupt brain activity momentarily in a specific brain region o Limitations – used only for short durations to examine brain areas o Powerful method for seeing which brain regions are necessary for specific psychological functions Spinal Cord – rope of neural tissue; runs inside hollows of vertebrae from just above pelvis into the base of the skull Functions – carry sensory information up to brain and carry motor signals from brain body parts below to initiate actions o coordination of reflexes 2 distinct tissue types: o gray matter – dominated by neuron’s cell bodies consists mostly of neuron bodies that have nonmyelinated axons and communicate only with nearby neurons o white matter – consists mostly of axons and fatty myelin sheaths that surround them consists mostly of myelinated axons that travel between brain regions Brain Stem - thicker, extension of spinal cord; more complex o Houses structures that control functions associated with survival, such as heart rate, breathing, swallowing, vomiting, urination and orgasms o Significant hit to region can cause death o Performs functions for head similar to spinal cord – gag reflex o Consists of medulla oblongata, pons, and midbrain o Contains reticular formation – network of neurons; projects up into cerebral cortex and affects general alertness; sleep and arousal involved in reducing and terminating different stages of sleep Cerebellum – a large, convoluted protubence at the back of the brain stem; essential for coordinated movement and balance motor learning and motor memory; “trained” by rest of nervous system and operates independently and unconsciously Ex: making plans, remembering events, using language, experiencing emotion Effects of damage to certain areas: o Back of cerebellum – walking o Bulging lobes on sides – limb coordination o Little nodes at bottom – head to tilt, balance problems, loss of smooth compensation of eye position for head movement Subcortical Structures Lie under the cerebral cortex Limbic System - serves as a border between older parts (brain stem and cerebellum) and newer part (cerebral cortex) Hypothalamus, hippocampus, amygdala Controls appetites, behaviors and emotions Thalamus - gateway to cortex; receives almost all incoming information, organizes it and relays it to the cortex Exception is smell; oldest sense; has direct route to cortex During sleep, it partially shuts the gate on incoming sensations while the brain rests Hypothalamus - brain's mastery regulatory structure; needed for survival Receives input from almost everywhere in body and brain, and it projects its influence to almost everywhere in body and brain Affects functions of many internal organs, regulating body temperature, body rhythms, blood pressure and blood glucose levels Involved in many motivated behaviors—thirst, hunger, aggression, lust Hippocampus – important role in formation of memories by creating new interconnections within the cerebral cortex with each new experience involved in how we remember the arrangements of places and objects in spaces important for navigating in environments (Maguire study of taxi drivers and volume of gray matter in hippocampus; did not conclude hippocampus changes with experience) Amygdala – (almond shape) located in immediately in front of hippocampus involved in learning about biologically relevant stimuli, such as those important for survival plays a special role in responding stimuli that elicit fear (evolved to protect animals from danger) involved in evaluating a facial expression’s emotional significance part of a system that automatically directs visual attention to the eyes when evaluating facial expressions imaging studies have found that amygdala activation is especially strong in response to a fearful face intensifies the function of memory during times of emotional arousal o ex: a frightening experience can be seared into memory forever, although memory might not be accurate o emotional arousal can influence what people attend to in their environments Basal ganglia – system of subcortical structures crucial for planning and producing movement; structures receive input from the entire cerebral cortex and send that input to the motor centers of the brain stem Through the thalamus, they also send that input to the motor planning area of the cerebral cortex Damage to basal ganglia o can produce symptoms that range from the tremors and rigidity of Parkinson’s disease to the involuntary writhing movements of Huntington’s disease o impair learning of movements and habits, such as automatically looking for cars before you cross the street nucleus accumbens – (part of basal ganglia), important for experiencing reward and motivating behavior o nearly every pleasurable experience involves dopamine activity in nucleus accumbens and makes you want the person you are experiencing; the more desirable objects are, the more they activate basic reward circuity in our brains Cerebral Cortex and Complex Mental Activity Cerebral Cortex – the outer layer of the cerebral hemispheres and gives the brain its distinctive wrinkled appearance (feels like soft-boiled egg) each hemisphere has its own cortex; in humans it’s pretty large and folded in against itself so it can fit in skull site of all thoughts, detailed perceptions, and complex behaviors enables us to comprehend ourselves, other people, and the outside world source of culture and communication each cerebral hemisphere has 4 lobes – temporal, occipital, parietal and frontal lobes Corpus callosum – a massive bridge of millions of axons, connects the hemispheres and allows information to flow between them Four Main Lobes Occipital Lobes – at the back portion of the head; holds primary visual cortex o Exclusively for vision, includes many visual areas o Primary visual cortex – largest of these areas; major destination for visual information o Visual information is typically organized for the cerebral cortex in a way that preserves spatial relationships. The image relayed from the eye is “projected” more or less faithfully onto the primary visual cortex o As a result, 2 objects near one another in a visual image will activate neurons near one another in the primary visual cortex. Surrounding the primary visual cortex is a patchwork of secondary visual areas that process various attributes of the visual image, such as colors, forms and motions Parietal Lobes (holds primary somatosensory cortex) o Devoted partially to touch o Labor divided between the cerebral hemispheres o Left – receives touch information from the right side of the body o Right – receives touch information from the left side of the body o In each lobe, this informational is directed to the primary somatosensory cortex – a strip in the front part of the lobe, running from the top of the brain down the sides o PSC groups nearby sensations; ex: sensations at fingers are near sensations on palms o Results in a distorted representation of the entire body – somatosensory homunculus – distorted because more cortical area is devoted to the body’s more sensitive areas, such as the face and the fingers Homunculus is based on brain mappings by neurologist Wilder Penfield; he created this mapping as he examined patients undergoing surgery for epilepsy; his studies provided important evidence about the amount of brain tissue devoted to each sensory experience o Involved in attention o Hemineglect – caused by stroke or damage to the right parietal lobe; people fail to notice anything on the left side even though their eyes work perfectly well; will do things/draw on the right side only (ex: put makeup only on right side of face) Temporal Lobes (holds primary auditory cortex) o Responsible for hearing o Has specialized visual areas (for recognizing detailed objects such as faces) o hippocampus and amygdala are a part of it o fusiform face area – at intersection of temporal and occipital lobes; much more active when people look at faces than other things; damage to area can cause impairments in recognizing people but not objects o in contrast, other regions of temporal lobe are more activated when looking at other objects Frontal Lobes (holds primary motor cortex) o Planning and movement o Primary motor cortex – rearmost portion of lobe; includes neurons that project directly to the spinal cord to move the body’s muscles o Responsibilities divided down middle of body (ex: left hemisphere controls right arm and right hemisphere controls left arm) o Prefrontal cortex – rest of frontal lobe; 30% of brain in humans; more complex than animals’, organization of prefrontal circuits make us more complex o Parts of it are responsible for directing and maintaining attention, keeping ideas in mind while distractions bombard people from the outside world, and developing and acting on plans o Entire prefrontal cortex is responsible for rational activity o Important for human social life such as understanding what people are thinking, behaving according to cultural norms, and contemplating one’s own existence o Provides sense of self and capacity to emphasize and feel guilty o Phineas Gage – provided basis for first theories of prefrontal cortex’s role in personality and self-control (1848) o got a rod through his head and frontal lobes; recovered but led to many personality changes; became fitful, indulging at times of grossest profanity, impatient when conflicts with his desires; “not the same Gage” o after a decade, health declined and started to have epileptic seizures and died a few months later (1860) o prefrontal cortex most damaged by rod o people with damage have disability to get along with others, not affect to memory or knowledge o Lobotomy – (1930s Antonio Moniz) a form of brain surgery that deliberately damaged the prefrontal cortex; o this was done b/c of significant increase of people in mental institutions; left them lethargic, emotionally flat, and easier to manage (done in 1940s and 50s) o he received the Nobel prize in 1949 o procedure phased out when medications for these were created Split Brain – a condition that occurs when the corpus callosum is surgically cut and the 2 hemispheres of the brain do not receive information directly from each other; damages gray matter have no immediate apparent problems; some had not affected patients in any way in a healthy person, the corpus callosum allows the hemispheres to communicate so that the right brain knows what the left is doing in a split-brain patient, the hemispheres are separated, so this communication cannot take place; hemispheres function as 2 different entities o this division allows researchers to independently examine the function of each hemisphere w/o the influence of the other; can provide info to and receive info from a single hemisphere at a time in split-brain patients, the right hemisphere has no discernable language capacity; left hemisphere dominant for language; o Ex: if sees 2 pictures at same time, one on left and right; patient will only report that only the picture on the right was shown; this is b/c the left hemi, with its control over speech, sees only the picture on the right side. It is the only picture they can talk about; right hemi is unable to make a response; but can still make a perception and left hemi won’t know what right one saw right = better with spatial relationships left = better with language produces 2 half brains; each half has its own perceptions, thoughts, and consciousness Experiment: person asked to arrange blocks in a square; when does it with left hand, controlled by right hemisphere, they do it effortlessly; when they do it with right hand, controlled by left hemisphere, they can’t do it very well; right hemi is much better with spatial relationships, which is why left hemi/right hand can’t do it Psych 3.3 How does the brain communicate with the body? Peripheral Nervous System Somatic nervous system (SNS) – transmits sensory signals to the CNS via nerves o Specialized receptors in the skin, muscles, and joints send sensory information to the spinal cord, which relays it to the brain o The CNS sends signals through the SNS to muscles, joints and skin to initiate, modulate, or inhibit movement Automatic Nervous System (ANS) – regulates the body’s internal environment by stimulating glands (such as sweat glands) and by maintaining internal organs (such as the heart) o nerves in the ANS carry somatosensory signals from the glands and internal organs to the CNS; these signals provide information about, for example, the fullness of your stomach or how anxious you feel o Sympathetic division – prepares your body for action if in a dangerous situation or if something makes you nervous, sexual arousal, stress the more aroused you are, the greater the sympathetic system’s dominance dilates pupils, relaxes bronchi, heart accelerates, strengthens heartbeat, inhibits activity in stomach and intestines, contracts blood vessels of internal organs o Parasympathetic division – it returns your body to its resting/normal state Contracts pupils, constricts bronchi, slows heartbeat, stimulates activity in stomach and intestines, dilates vessels DO NOT NEED TO KNOW BELOW Endocrine System A communication network that influences thoughts, behaviors and actions Slower and uses hormones compared to nervous system Hormones – chemical substances released into the bloodstream by the ductless endocrine glands, such as the pancreas, thyroid, and testes or ovaries o Once released, they bind to receptor sites and influences the tissues; b/c they travel through bloodstream, it can take seconds to hours to take effect Gonads – the main endocrine glands influencing sexual behavior; the testes and ovaries o Adrogens – more prevalent in males, testosterone o Estogens – more prevalent in females, estradiol and progesterone o These hormones influence the development of secondary sex characteristics (ex: breast development, facial hair) o Influence sexual behavior o Men only need a minimum amount of testosterone to perform sexually o Women’s sexual behavior may have more to do with androgens than estrogens Women with higher blood levels of testosterone report greater interest in sex, and testosterone injections increase women’s sexual interest after removal of uterus o Women’s sexual activity not particularly linked to menstrual cycle o when they are ovulating, heterosexual women find men who look/act more masculine more attractive and they show greater brain activity in regions associated with reward while viewing attractive male faces; have lower self-esteem and greater motivation to find a partner during that time, possibly increasing their efforts to look attractive Endocrine System and Nervous System Actions Are Coordinated they are fully integrated and interact to facilitate survival; use information from the organism’s environment to direct adaptive behavioral responses endocrine system is under control of nervous system; brain interrupts external and internal stimuli, then sends signals to the endocrine system; endocrine system responds by initiating various effects on the body and on behavior endocrine system primarily controlled by hypothalamus via signals to the pituitary gland – located at the base of the hypothalamus; master gland of body o neural activation causes the hypothalamus to secret a particular ne of its many releasing factors; the releasing factor causes the pituitary to release a hormone specific to the factor, and the hormone travels through the bloodstream to endocrine sites throughout the body o once the hormone reaches the target sites, it touches off the release of other hormones, which affects body reactions and behavior o pituitary gland controls all other glands and governs major processes such as development, ovulation, and lactation by releasing hormones in bloodstream Growth Hormone (GH) – a hormone released from the pituitary gland, prompts bone, cartilage, and muscle tissue to grow and helps them regenerate after injury o used by athletes to increase body size and strength o stimulates the eating of protein by making it especially enjoyable Psych 3.5 Genetic Basis of Psychological Science Human Development Has a Genetic Basis Gene expression – whether a particular gene is turned on or off; environmental factors may affect it Determines body’s physical makeup and developments throughout life Genome – master blueprint that provides detailed instructions for everything in body Chromosome – structures within the cell body that are made up of DNA, segments of which comprise individual genes; 23 pairs in a cell, one from mom and one from dad Gene – the units of heredity that help determine the characteristics of an organism; a particular sequence of molecules along a DNA strand Specifies an exact instruction to manufacture a distinct polypeptide; 1 or more polypeptides make up a protein – the basic chemicals that make up the structure of cells and direct their activities Human Genome Project – found people have fewer than 30,000 genes Heredity and Reproduction Gregor Mendel (1866) studied inheritance; developed an experimental technique, selective breeding – strictly controlling which plants bred with other plants; single-gene experiment o Selected pea plants with only purple or white flowers and cross-pollinated them; 1 generation of offspring tended to be completely white or purple; allowed each plant to self-pollinate into a 2ndgeneration revealed a different pattern: 75% purple flowers and 25% white flowers; 3:1 ratio repeated itself; held true for other characteristics o Found out some genes are dominant or recessive Dominant gene – a gene that is expressed in the offspring whenever it is present Recessive gene – a gene that is expressed only when it is matched with a similar gene from the other parent Genotype – an organism’s genetic makeup; determined at moment of conception; never changes Phenotype – organism’s observable physical characteristics; always changing; environment and genetics affects it Polygenic characteristic – trait is influenced by many genes (and environment) o Ex: skin color, height, intelligence effected by many genes Genotypic Variation and Sexual Reproduction Zygote – produced during fertilization of an egg and sperm’ contains 23 pairs of chromosomes; half from dad and half from mom o Grows through cell division; 2 stages; chromosomes duplicate, and cell divides into 2 cells Mutation – alterations in DNA; most are benign and have little influence on organism; can be an advantage or disadvantage; adaptive or maladaptive; mutation may spread if it is advantageous to the organism and more likely to survive Industrial melanism - moths adapted to being darker because it was advantageous and it was harder for predators to see them against darker backgrounds Sickle-cell disease – genetic disorder that alters the bloodstream’s processing of oxygen; can lead to pain, organ and bone damage and anemia; occurs mainly in African Americans; recessive gene so has to receive it from both parents to get it Sickle-cell trait – those who receive a recessive gene from only 1 parent Recessive genes do not interfere with most people’s health Genes Affect Behavior Behavioral genetics – the study of how genes and environment interact to influence psychological activity; provides important info about the extent to which biology influences mind, brain, and behavior Twin studies compare similarities between different types of twin to determine the genetic basis of specific traits Monozygotic twins – (identical twins) result from 1 zygote (fertilized egg) dividing in 2; each new zygote has the same chromosomes and the same genes on each chromosomes Dizygotic twins – (fraternal twins) result when 2 separately fertilized eggs develop in the mother’s womb simultaneously Minnesota Twin Project – identifies more than 100 pairs of identical and nonidentical twins, some raised together and some raised apart; general finding was that identical twins, whether they were raised together or not, were likely to be similar; some argued that most of them were raised to relatively similar environments Heredity – the transmission of characteristics from parents to offspring by genes Heritability – the proportion of the variation in some specific trait in a population, not in an individual, that is due to genetics; the trait cannot be due to environment or random choice o Heritability for a trait depends on variation – the measure of overall differences among a group of people for that particular trait o To perform a heritability analysis, there must be a variation in the population o Ex: among American women there is a heritability of .60 Social and Experimental Contexts Influence Genetic Expression Nature and nurture together affect behavior New Zealand study – gene that controls MAO is called MAOA and comes in 2 forms: one leads to higher levels of MAO and the other leads to lower levels of MAO; found that boys with low-MAOA gene were susceptible to effects of early-childhood mistreatment; boys with high-MAOA gene are much more likely to be convicted of a violent crime Epigenetics – looking at the processes by which the environment affects genetic expression; found that various experimental exposures do not alter DNA, but they do alter DNA expression making it more/less likely a gene will be expressed o Ex: living under stress or consuming a poor diet makes some genes more/less active Genetic Expression Can Be Modified Changing even a single gene can dramatically change behavior Transgenic mice (genetically modified) Optogenetics – research technique that provides precise control over when a neuron fires; this enables researchers to better understand the causal relationship between neural firing and behavior o Combines the use of light with gene alterations; genes are altered to change a particular subpopulation of neurons in the brain o Allows researchers to show that activating or deactivating specific neurons causes changes in brain activity or behavior
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