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PSYA02H3 (961)
Chapter 12


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Steve Joordens

CHAPTER 12: Lifespan Development - Major developmental periods of life: prenatal development, infancy and childhood, adolescence, adulthood and old age - Growing older is matter of changing personally, intellectually, and socially - Cross-sectional study: a study of development in which individuals of different ages are compared at the same time usually more convenient and avoid prob of repeatedly testing same individs subtle prob in interpretation - Longitudinal study: a study of development in which observations of the same individuals are compared at diff times of their lives 1. Prenatal Development - Prenatal period: the nine months b/w conception and birth divided into 3 developmental stages: zygotic, embryonic, and fetal length of normal pregnancy is 266 days or 38 weeks - During this time, development depends on two factors genetic contrib. From egg and sperm that determine the genotype; child develops a single source of genetic instructions epigenetic modifications; cells chemical enviro moderates the expression of the genetic code - All cells have the same genetic content, but they perform diff functions and become diff types of cells some factor must direct the mech of replication during prenatal period so cells that are genetically identical develop along diff paths e.g. deactivation of X chromosome; found in women; limits total amount of proteins prod by genes located on the X chromo - X chromo deactivation is example of epigenetic modification modification of cell inheritance that is not due to alterations of the DNA seq itself these changes include the way DNA molec is folded w/i other proteins, chemical changes in the structure of the nucleotide, and how info is mapped on the genome - While the genetic info remains the same all thru-out a persons development, the cells become specialized STAGES OF PRENATAL DEVELOPMENT - Starting point: union of sperm and egg (conception) - 1)Zygote stage: the first stage of prenatal development during which the zygote divides many time and the internal organs begin to form lasts about two weeks by end of first week, zygote consists of about 100 cells arranged into two layers one for skin, hair, nervous system and sensory organs; the other for digestive and respiratory systems and glands near the end of this stage, a third layer forms for muscles and the circulatory and excretory system - 2)Embryonic stage: the second stage of prenatal development, beginning at about two weeks and ending at about 8 weeks after conception, during which the heart begins to beat, the brain starts to function, and most of the major body structures begin to form zygote becomes an embryo and development is very rapid end of this stage, major features have formed; arms, hands, fingers, legs, toes, shoulders, head and eyes the embryo can react reflexively to stim delicate chemical balance; prone to damage from external chemical influences teratogens: substances, agents, and events that can cause birth defects - Sexual development begins during embryonic stage ; 23 rdchromo determines sex male XY; female XX early in prenatal development, embryo develops gonads that will either be testes or ovaries Y chromo releases chem. Signal to make gonads become testes; no Y, makes ovaries - Presence or absence of testes determines the development of the other sex organs if present, they begin to secrete hormones androgens: the primary class of sex hormones in males; most imp is testosterone bring about development of male internal sex organs, penis, and scrotum development of female sex organs (uterus, vagina, & labia) occur naturally; not stim by hormone - 3)Fetal stage: the third and final stage of prenatal development, which lasts for about 7 months, beginning w/ the appearance of bone tissue and ending with birth at the end of 2 nd month, fetus is about 4 cm long and 30g end of 3 rdmonth, development of major organs is done and bones and muscles begin to develop; 8cm and 90g; may show movement esp kicking th end of 4 month, 15 cm and 170 g; sleeping and waking up regularly; stronger movements felt by mother; heartbeat loud enough to be heard w/ stethoscope sound and light sensitivity enlarge in few weeks th 6 month, more than 30cm and 700g 7 month is critical cuz it can be born prematurely w/ little chance of survival; would require breathing help during last 2 months, fetus gains weight at a rate of about 250g per week end of this period, fetus is about 50cm long and around 3.5 kg fetus is ready to be born THREATS TO NORMAL PRENATAL DEVELOPMENT - Imp factor in fetus development is the mothers diet; food she eats is fetus only source of nutrition - Teratogens can also cause birth defects psychs interested in birth defects caused by drugs; depends on behav of mother certain antibiotics, esp in large quantities over long period of time, can prod fetal defects e.g. tetracycline causes teeth discolouration and bone irreg - If the mother takes cocaine, increases chances of premature birth, low birth weight, and smaller- than-normal head circumference also interferes w/ neural development long-term consequences in areas of arousal and attention some babies born addicted; show withdrawal symptoms such as hyperactivity, irritability, tremors and vomiting - Smoking can also affect the fetus CO2 from the smoke reduces the fetus oxygen supply reduced oxygen levels are most harmful in the last half of pregnancy when the fetus is developing most rapidly and has the greatest oxygen demand increased rate of miscarriage, low-birth weight, increased chance of premature birth, more births by C-section may also lead to lowered arousal levels in newborns, cleft palate, deficits in ability for newborns brain to process speech sounds, and behav problems in adolescence - Studies based on alcohol use during pregnancy pre- and postnatal growth deficits, deformations of the eyes and mouth, low brain mass, other brain and central nervous system abnormalities, and heart deformation fetal alcohol syndrome (FAS) even if these children are raised in a healthy enviro w/ regular, nutritional meals, their intellectual development still falls short of that of normal children drinking as little as 2 oz in the first months of pregnancy can still cause some symptoms of FAS - Some teratogens are more difficult to avoid include industrial/agricultural pollution pesticides, air pollution, etc. led researchers to seek anti-teratogens to reduce risks 2. Physical and Perceptual Development in Infancy and Childhood - Infant and toddler refer to babies up to the age of 2 years newborns are helpless and dependent on their caregivers but do not passively wait for them MOTOR DEVELOPMENT - Normal motor development seems to follow a distinct pattern; dictated by maturation of muscles and the nervous system maturation: any relatively stable change in thought, behav, or physical growth that is due to the aging process and not to experience although children progress at diff rates, they follow the same maturation pattern - At birth, infants most imp movements are reflexes automatic movements in response to specific stim rooting, sucking, and swallowing e.g. rooting = if you touch a babys cheek, it will turn towards the direction of the touch if an object makes contact with the babys lips, it will start sucking if milk or any other liquid enters the babys mouth, it will start swallowing - Development of motor skills = maturation of the childs nervous system and practice nervous system is not complete at birth; considerable growth occurs in the first few months which is associated w/ IQ in later childhood imp changes in brain structure occur throughout the lifespan as a result of exp - Partic movements have to await the development of necessary neuromuscular systems - Phys development of the nervous system depends on the ways the baby moves while interacting w/ the enviro more complex movements depend on further development of the nervous system, creating an interplay b/w motor and neural development PERCEPTUAL DEVELOPMENT - Fetal exp w/ sensory stim can prepare the way for the newborns exp Kisilevsky and colleagues found that playing a recording of the mothers voice outside her abdomen increased the heart rate of the fetus, while playing a strangers voice did not - At birth, childs sense are already working auditory system can detect sounds; startled reaction when presented a loud sound bright lights will elicit eye closing and squinting pinch will cause crying; sense of touch works if tilted backwards, baby will stiffen and flail their arms; showing a sense of balance sense of taste works too; show preference of what they drink thru facial exp have an early developing ability to distinguish odors; element of mother-infant bonding e.g. infants can tell who their mother is from other lactating women by breast odou
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