Brain and Behavior Study Guide Exam 2 Genetics Heritability estimate of how much of the variance in a characteristic within a population is due to differences in heredity genes o Twin studies monozygotic MZ identical vs dizygotic DZ fraternal do adoption studies to see if behavior is environmentally based or inherited one major problem could be due to prenatal environment instead of inheritability o Multiplier effect genes predispose you to behaviors and to different treatments by others Genetic terms to know What started out as potentially small effect of genes ends up having a huge behavioral result leading to an overestimation of heritability o Transcription from DNA to RNA o Translation from RNA to proteins o Chromosome contains DNA we have 46 22 paired and 2 sex chromosomes DNA deoxyribonucleic acid in the nucleus RNA ribonucleic acid o Gene sequence of DNA that contains information on hereditary characteristics Homozygous person with identical sets of genes on the 2 chromosomes AA Heterozygous person with unmatched pair of genes on the 2 chromosomes Dominant a gene that shows strong effect in heterozygous or homozygous Recessive a gene that shows strong effect only in the homozygous condition or aa Aa a condition A Sex linked genes the genes on the sex chromosomes X and Y More commonly on the X chromosome because it is much larger Disorders more often occur in males because they only need the trait to Examples display it while females require the trait on both X chromosomes muscular dystrophy fragile X syndrome red green color blindness hemophilia Sex limited genes present in both sexes but has an effect only mostly in one sex Genes are turned on under influence of sex hormones Examples chest hair in men breast size in women Evolution descent with modification o Natural selection how species acquire their adaptive characteristics process by which inherited traits that confer a selective advantage increase an animal s likelihood to survive and reproduce become more prevalent in a population variability occurs due to 1 mixing of DNA recombination and 2 random mutations o Artificial selection when humans alter the natural course of evolution by choosing a particular phenotype to eliminate ex Fish size in lakes o Similarity between species suggest a common ancestor Epigenetics changes in phenotype appearance or gene expression caused by mechanisms other than changes in the underlying DNA sequence o you can alter the probability that a gene will be expressed without actually altering the DNA itself Drug Interactions all drugs of abuse cause dopamine release in the nucleus accumbens Stimulants increase dopamine serotonin and norepinephrine levels increase excitement activity alertness mood and decrease fatigue o Cocaine blocks reuptake of dopamine serotonin and norepinephrine They bind to the DAT which blocks the reuptake of dopamine high DAT dopamine transporter removes excess dopamine from the Stored dopamine is then depleted and causes depression crash o Ritalin prescribed for ADHD blocks the reuptake of dopamine gradual effect o Ecstasy stimulant even at low doses increases dopamine and norepinephrine release At high doses it stimulates serotonin release by reversing the serotonin synapse instead of instant high transporter Causes hallucinations and decrease in depression and anxiety Increases release of posterior pituitary hormones oxytocin vasopressin Serotonin syndrome too much serotonin released into body because of too much of a serotonin agonist or because of mixing drugs that all act in some capacity as serotonin agonists o Can be deadly when MAOIs are mixed with certain drugs especially ecstasy o Can be life threatening Nicotine Increases dopamine release in nucleus accumbens stimulates nicotinic Ach receptor on VTA neurons thereby exciting them o Present in tobacco o Cells become less responsive to it after repeated use Opiates bind to opioid receptors aka endorphin receptors in both the nucleus accumbens and on the GABA neurons ex morphine methadone heroin o Methadone drug taken to combat opioid addiction on its own it is highly addictive Taken as a pill so it enters slowly and is digested slowly no rush or crash much more controlled Combined with naloxone blocks opioid receptors so that addicts take it correctly taken orally instead of injected snorted etc Cannabinoids aka marijuana indirectly increase dopamine in nucleus accumbens dissolves in body fats and leaves slowly o intense sensory experiences and illusion of time passing slowly Hallucinogens Stimulate serotonin 2A receptors at inappropriate times or for longer than can impair memory and cognition o can have medicinal uses usual ex LSD shrooms PCP o Distorts perception hallucinations Alcohol increases stimulation at both dopamine and opiate receptors including in nucleus accumbens o Glutamate receptor antagonist depressant o gets into membrane of cells and messes things up o too much alcohol damages liver and impairs judgment o Alcoholism continued use of alcohol despite medical or social harm even after having made a decision to quit or decrease drinking Third largest health problem behind cancer and heart disease Two types of alcohol addiction Type 1 A gradual onset fewer genetic relatives with issue less severe equal numbers of men and women suffer from it Typer 2 B early and rapid onset genetic relation men outnumber women often severe and associated with criminality o Effects of genes on alcoholism Dopamine receptor the longer version of the gene makes less sensitive receptors Breaks down dopamine people with this gene type experience stronger craving for alcohol after one drink compensates for less than normal reinforcement from it one enzyme more active than the other People break down dopamine faster and therefore there is less reinforcement from things that should increase dopamine Tend to be more impulsive reward now and disregard big picture o Risk factors Sons of alcoholics Impulsive easily bored outgoing childhood Higher tolerance for alcohol Decreases stress Smaller amygdala on the right o Medications Antabuse antagonizes the acetaldehyde dehydrogenase AD which makes you sick when you consume alcohol vomiting impaired breathing etc Moderately effective must be committed to quitting Naloxone binds to opioid receptors and decreases pleasure in alcohol Acamprosate helps with getting through physical symptoms of withdrawal Glutamate receptor antagonist Tolerance need more of the drug to get the
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