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Chapter 12

Chapter 12-lifespan development.docx

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University of Toronto Scarborough
Caroline Barakat

Chapter 12 Lifespan DevelopmentDiscussing the physical intellectual and social changes that we go through as we age and some problems associated with abnormal development Crosssectional study individuals of different ages are compared at the same timeLongitudinal study a study of development at which the same people are observed at different times in their livesPhase Age Prenatal Conception through birth Rapid physical development to nervous system and body Infancy Birth 2 Motor development and attachment to primary caregiver Childhood 18 months 12 years Increasing ability to think logically and reason abstractlyrefinement of motor skills peer influences Adolescence 13 20 Thinking and reasoning becomes more adult like identity crisis peer influences Adulthood 2065 Lovecommitted relationship career stability and then decrease in physical abilitiesOld age 65 death Reflection on lifes work and accomplishmentsprepare for death death PRENATAL PERIOD nine months between conception and birth the period is separated ino three developmental stages zygotic embryonic and the fetal phases Genetic contribution of the egg and sperm that determines the genotype of the new individual Prenatal development is not a matter of cellular replicationAll cells of an individual have the same genetic content they differ blood cells vs neurons and muscle cells200 different types of cell develop from the union of a sperm and zygote X chromosome inactivation important because it limits the total amount of proteins produced by genes located on the X chromosome Without this the metabolism of a female would be different from a maleonly one X chromosome X chromosome inactivation is a form of epigenetic modification a modification of cell inheritance that is not due to alterations of the DNA sequence Epigenetic modifications produce a second factor of early development and illustrate that the cells chemical environment moderates the expression of its genetic code Even though the genetic information contained within a person is the same the reproducing cells become specialized as blood cells neurons and muscle cells Prenatal Development Zygote stage 2 weeks he first state of prenatal development during which the zygote divides many times and the internal organs begin to form By the end of the first week the zygote consists of about a hundred cells many of the cells ar arranged into layers to accommodate for the skin hair nervous system and sensory organsetc near the end of this stage a third layer of cells that will eventually develop into muscles and circulatory and excretory systemsEmbryonic Stage 28 weeks second stage of prenatal development beginning about two weeks and ending about eight weeks after conception during which the heart begins to beat the brain starts to functionand most of the major body structures begin to form Zygote turns into an embryo and development occurs at a rapid pace Heart beats brain and spinal cord function most of the major body structures begin to form Major body features are visible arms hands fingers legs toes shoulders head and eyes Embryo can react to stimulation Embryo is susceptible to external chemical influences including alcoholdrugs and other toxins known as teratogens Teratogens are substancesagents and events that can cause birth defects Beginning of sexual development occurs during the embryonic stage Female contributes the x chromosome and the male contributes the y xx female and xymaleThe embryo develops gonads that develop later into ovaries or testesIf a y chromosome is present the gene located on it causes a chemical signal that will produce testesif not ovaries will be produced from the gonads Androgens primary class of sex hormones in males The most important androgen is testosterone Androgens bring about the development of male sex organspenis and scrotum Female sex organs develop naturally and DONT NEED TO BE CREATED BY THE STIMULATION OF A HORMONE Fetal stage final period of prenatal development and lasts about seven months It officially begins with the appearance of bone cells and ends with birthnd 2 month fetus is 4 cm in length and weights 30g rd 3 month development of major organs is completed and the bones and muscles are beginning to develop8 cm and 90gth 4 month 15cm long weighs 170 g it is now sleeping and waking regularly Fetal movements become strong enough to be felt by the motherand the heartbeat is loud enough to be heard by a stethoscopeth 6 month fetus grows to more than 30 cm long and weighs 700 g the seventh month is critical because if it is born prematurely it has a fair chance of surviving During the last two months of prenatal development the fetus grows rapidly and gains nearly 250g per week The fetus is about 50 cm long and weighs about 35 kg at the end of this periodThe fetus can be born at this pointThreats to Normal Prenatal DevelopmentMothers diet is an important factor food she eats is the fetuss source of nutrition If she is malnourished the fetuss nervous system may develop abnormally and intellectual deficits may result Teratogens can cause birth defects Use of cocaine can create premature birth low birth weight and smaller than normal head circumference and can affect neural development as well Smoking carbon monoxide reduces the supply of oxygen to the fetus Reduced oxygen levels are harmful during the last two months of pregnancy when the fetus is developing quickly and the demand for oxygen is highincreases miscarriages low birth weight increased chance of premature birth caesarian section births Chemical and biological toxins agricultural pollution can lead to birth defects as well Physical and Perceptual Development in Infancy and ChildhoodMotor DevelopmentNormal motor development follows distinct patterns that seem to be dictated by the MATURATION of the muscles and nervous systems Maturation is changes in thought behaviour or physical growth that is due to the ageing process and not to experience Children tend to develop according to the same basic maturation pattern
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