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Chapter 3

PSY100 Psychological Science (3rd Ed.) Textbook Notes Chapter 3

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Alison Luby

CHAPTER 3BIOLOGICAL FOUNDAITONS Genetics behavior geneticists study how genes and environment interact to influence psychological activity use two methods to assess the degree to which traits are inherited twin studies and adoption studies Monozygotic Twins Identical Twins results from one zygote fertilized egg dividing in two each twin has same chromosomes and the same genes on each chromosomeDizygotic Twins Fraternal Twins result from two separately fertilized eggs developing in the mothers womb simultaneously no more similar genetically than any other pair of siblingsMinnesota Twin Project 1990 by Bouchard showed that identical twins raised together or not were likely to be similar critics says that the adopted twins in the project were raised in similar environments bc agencies to try match child to adoptive home some critics say similarities are coincidental Evidence suggests twins raised apart may be more similar to twins raised together when parents encourage individuality Adoption Studies compare similarities between biological relatives and adoptive relatives eg similarities among nonbiological adopted siblings have more to do with environment than genes growing up in same home actually has little influence on many traits like personalityHeredity the transmission of characteristics from parents to offspring by the means of genes Heritability statistical estimate of the variation caused by differences in heredity in a trait within a populationDepends on the variation the measures of the overall difference among a group of ppl for that particular traitEgif population has heritability of 06 for height than 60 of height variation among individuals within the population is genetic heritability value for having two legs is zero almost everyone has two legs In longitudinal study of criminality Caspi 2002 followed New Zealanders from birth hypothesized that the enzyme monoamine oxidase MAO determines susceptibility to effects of maltreatment boys with lowMAO gene produces less MAO more likely to be violent criminals with maltreatment but no violence without maltreatment effects of maltreatment had less influence on those with highMAO gene knockout mice research mice in which genes had been rendered inactive to study genes functionsNervous System Neurons basic unit of the nervous system operates through electrical impulses which communicates w other neurons through chemical signals receive integrate transmit information in the nervous systemSensory Neurons Affrent neurons detect information from the physical world and pass information along to brain through the spinal cord nerves that provide information from muscles are called somatosensoryMotor Neurons Effrent neurons direct muscles to contract or relax producing movementInterneurons communicate only with other neurons typically within specific brain region Neuron Structure dendritecell bodyaxonterminal buttonssynapse Dendrites branchlike extensions of the neuron that detects information from other neuronsCell body informationfrom other neurons is collected and integratedprocessedAxon transmit electrical impulses nerve refers to bundle of axons that carry info between brain and bodyTerminal Buttons nodules that release chemical signals from neuron to the synapsesynaptic cleft Synapse site for chemical communication bw neurons which contains extracellular fluid neurons do not touchMyelin Sheath fatty material made of glial cells that insulate axon and allows for fast movement of electrical impulse along axonNodes of Ranvier gaps of exposed axon bw myelin sheath when action potentials are transmitted Resting membrane potential electrical charge of neuron when it is not active charge inside neuron is more negative than outside polarization is the change of the electrical charge inside and outside the neuronIon channels and sodiumpotassium pump contributes to polarization Na and K ions contribute to resting potential Action potential Neural Firing neural impulse that passes along the axon and causes the release of chemicals from terminal buttonsExcitatory chemical signals depolarize cell membrane increase likelihood the neuron will fire inhibitory chemical signals hyperpolarize the cell more negative decreasing likelihood of neuron firing Propagation when depolarization moves along axon like a wave sodium ion channels open successively action potential skips quickly bc of myelin sheath recharged at each node of RanvierDemyelination leads to multiple sclerosis MS
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