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SUSS PSY 207 STUDY UNIT 2 (CHAPTER 4.1 and 4.2 Prenatal Development and…

- - - - 2. The Embryonic Period
        
        Occurs from 3rd - 8th week.
        
        Organogenesis occurs. It is a process in which every major organ takes shape, in at least a primitive form, develops. Such developments include:
        
        The heart is beating four weeks after conception.
        
        Primitive nervous system emerges during the 2nd month.
        
        Sexual differentiation begins during the 7th and 8th weeks.
        
        Blastocyst differentiates into different layers:
        
        Outer layer development includes the chorion membrane which would progress to form the placenta. A placental barrier is also formed to protect the developing child from harmful substances in the mother’s bloodstream.
        
        Interior of the blastocyst give rise to other cell structure which would develop into specific tissues and organ
      - 3. The Fetal Period
        
        Last from week 9 to birth
        
        In the 3rd month, distinguishable external sex organs appear, and bones and muscles develop; fetus begins to move.
        
        Between the 10th and 20th week, neurogenesis (the rapid proliferation of neurons) occur; neurons then engage in migration to form specialised functioning units e.g. into visual or auditory neurons.
        
        Age of viability is about 23 weeks after conception; at this age, the fetus has a chance of surviving outside the womb.
      - 1. The Germinal Period
        
        Occurs in the first 2 weeks
        
        The zygote divides multiple times through mitosis, forming the blastocyst.
        
        At the end of week 1, the blastocyst implants into the uterus wall.
  - - - Teratogens: Factors to consider
        
        Dosage and duration. The greater the level of exposure and the longer the exposure to a teratogen, the more likely it is that serious damage will occur
        
        Genetic makeup. Susceptibility to harm is influenced by the genetic makeup of the unborn child as well as the mother’s genotype. Some fetuses are more (or less) resistant to teratogens and some mothers are more (or less) able to detoxify teratogens.
        
        Critical period. The effects of a teratogenic agent are worst during the critical period when an organ system grows most rapidly
        
        Environment. The effects of a teratogen depend on the quality of both the prenatal and the postnatal environments.
      - Types of teratogens
        
        Drugs: Thalidomide
        
        Thalidomide is a drug used widely in the late 1950s to relieve morning sickness
        
        Thalidomide had specific effects on development, depending on which structures were developing when the drug was taken.
        
        Taking thalidomide during the first two months of pregnancy resulted in stunted limbs or deformed sense organs in the unborn baby.
        
        If the mother waited until 35 or 36 days after conception before using thalidomide, her baby was usually not affected.
        
        Tobacco
        
        Smoking restricts blood flow to the fetus and increases the risk of a miscarriage, premature birth, and low birth weight.
        
        Babies of smokers are also more susceptible to respiratory, cognitive and conduct problems.
        
        Heavier smoking also raises the risk of sudden infant death syndrome (SIDS), in which a sleeping baby suddenly stops breathing and dies.
        
        Alcohol
        
        Alcohol readily crosses the placental barrier and disrupts neural development.
        
        The most severe effect of alcohol is a cluster of symptoms called Fetal alcohol syndrome (FAS), which causes damage to the central nervous system, resulting in:
        
        Low IQ scores (many are mentally retarded)
        
        Hyperactive behaviour and attention deficits.
        
        Mental health problems later in life
        
        Distinct facial abnormalities
        
        Diseases and Infections
        
        Maternal rubella can lead to blindness, deafness, heart defects and mental retardation. It is most dangerous during the first trimester when the ears, eyes, heart and brain are rapidly taking form.
        
        Sexually transmitted infections such as HIV simplex and syphilis can cause damage to the eyes and brain.
        
        HIV-infected mothers can transmit the virus to their babies
        
        (1) prenatally, if the virus passes through the placenta;
        
        (2) perinatally, when blood may be exchanged between mother and child as the umbilical cord separates from the placenta; or
        
        (3) postnatally, if the virus is transmitted during breast-feeding
        
        Environmental Hazards
        
        Radiation from X-rays and cancer treatments can cause mutations, spontaneous abortions and various birth defects
        
        Pollutants
        
        Prenatal exposure to heavy metals (e.g. lead) is linked to premature birth, low birth weight, and impaired intellectual functioning.
        
        Prenatal exposure to other pollutants such as polychlorinated biphenyls (PCBs) are also associated with poor reflexes in infancy and later learning difficulties.
    - - Emotional condition
        
        Chronic maternal stress can result in premature birth or stunted prenatal growth, leading to low birth weight.
        
        Acute maternal stress during the first trimester is linked to an increased likelihood of developing schizophrenia.
        
        Maternal depression during pregnancy may contribute to motor delays in new-borns.
      - Nutritional condition
        
        Maternal malnutrition affects prenatal development differentially, depending on when it occurs.
        
        Malnutrition in the 1st trimester can disrupt the formation of the spinal cord, resulting in fewer brain cells or causing stillbirth.
        
        Malnutrition in the 3rd trimester results in smaller neurons, a smaller brain, and a physically smaller child.
      - Age
        
        Typical and safest age range for pregnancy is from about age 20 to 40 years.
        
        Young mothers (19 years of age or younger) have higher rates of birth complications such as premature deliveries and stillbirths.
        
        Older women have increased risk of miscarriage, stillbirth and low birth weight babies.
- - - - Types of study
        
        Adoption Studies
        
        Adoption studies examine if children adopted early in life are psychologically similar to their biological parents, whose genes they share, or are they similar to their adoptive parents, whose environment they share.
        
        If adopted children resemble their biological parents, genetics influence is stronger.
        
        Criticisms of Adoption studies
        
        A criticism of such studies is that the prenatal environment provided by the biological mother may also influence development.
        
        Family studies
        
        Family studies are Complex studies involving siblings who have different degrees of genetic similarity – twins, siblings, half-siblings, unrelated step-siblings
        
        Twin Studies
        
        Twin study involves determining whether identical twins reared together are more similar to each other in traits of interest than fraternal twins reared together.
        
        More complex twin studies include not only identical and fraternal twin pairs raised together but also identical and fraternal twins raised apart
        
        If genes matter, identical twins should be more similar
        
        Limitations of twin studies:
        
        identical twins could be more psychologically similar than fraternal twins, even if they were separated at birth because they shared a more similar prenatal environment than fraternal twins did.
        
        Second, the fact that identical twins are often treated more similarly than fraternal twins could explain their greater psychological similarity. More likely, twins’ similarities result in their being treated similarly
      - Heritability
        
        is the proportion of all the variability in the trait within a large sample of people that can be linked to genetic differences among those individuals.
        
        E.g. To say that measured intelligence is heritable, then, is to say that differences in tested IQ among the individuals studied are to some degree attributable to the different genetic.
        
        Three factors that contribute to differences in individuals:
        
        Genes
        
        Shared environmental influences
        
        Non-shared environmental influences
      - Estimating gene Influences
        
        Concordance rates
        
        It is the percentage of pairs studied in which if one member has the characteristic, the other does as well.
        
        e.g. If one of the identical twins develops schizophrenia, what is the likelihood of the other twin also developing schizophrenia?
        
        Correlation coefficients
        
        Researchers also calculate the correlation coefficients for characteristics that can be present in varying degrees
  - - - Passive gene-environment correlations
        
        Parents provide both genes and home environment
        
        e.g. Extraverted parents not only transmit their “extraverted” genes to their children but also, because they are extroverted, create a highly extraverted home environment—inviting their friends over, taking their children to social gatherings, etc. The combination of “extraverted” genes and an extroverted environment may make their children more extroverted than they would otherwise be
      - Evocative gene-environment correlations
        
        Individual’s personality evokes reactions from others.
        
        e.g.The smiley, sociable baby is likely to evoke more smiles and social stimulation—and more opportunities to build social skills—than the wary, shy baby.
      - Active gene-environment correlations
        
        Children’s genotypes influence the kinds of environments they seek.
        
        an e.g. The individual with a genetic predisposition to be extroverted is likely to go to parties, invite friends over, join organizations, collect Facebook friends, etc.