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Chapter 12

Chapter 12 .docx

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Queen's University
PSYC 100
Ingrid Johnsrude

Textbook readings 2 Week 15: Chapter 12 Prenatal Development - Prenatal period extend over the 9 months between conception and birth, split into 3 developmental stages: zygotic, embryonic, and fetal - Zygote stage: first stage of prenatal development, during which the zygote divides many times, and internal organs begin to form. - Embryonic stage: second stage of development, beginning at about 2 weeks and ending at 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 - Teratogens: substances, agents and events that can cause birth defects - Normal pregnancy is about 266 days/38 weeks - In mammals, theres 200 different types of cells, all that develop from sperm and egg - X Chromosome inactiviation is an example of a factor that directs the mechanisms of replication during the prenatal period so that cells that are genetically identical will develop along different paths. - Inactivation of one of the X chromosomes is important because it limits the total amount of proteins produced by genes located on the X chromosome. Without this limit, the metabolism of a developing female would be different from that of a developing male (who only has one X chromosome) - X chromosome inactivation is an example of epigenetic modification, a modification of cell inheritance that is not due to alterations of the DNA sequence itself - Epigenetic changes include the way the DNA molecule is folded within other proteins Stages of prenatal development - During zygote stage: the zygote (single new cell formed at conception) divides many times and the internal organs begin to form. At the end of the week, the zygote has about 100 cells. - Many cells are arranged into 2 layers, one for skin, hair, nervous system, and sensory organs, and the other for the digestive and respiratory systems and glands. - At the end of the stage, a 3 layer of cells appear that will eventually develop into muscles and circulatory and excretory systems - Embryonic stage: begins 2 weeks and ends about 8 weeks after conception - Zygote is transformed into an embryo - A month after conception, a heart has begun to beat, a brain and spinal cord have started to function and most major body parts are starting to form. - At the end of this stage, the major features are discernible - Beginning of sexual development starts during the embryonic stage rd - 23 chromosome pair determines the sex of the embryo - female partner contributes an X chromosome to this pair at conception and the male partner contributes either an X or a Y chromosome - early in development the embryo develops gonads that will either become ovaries or testies - the presence of absence of testes determines the development of the other sex organs - if testes are present, they begin to secrete a class of sex hormones known as androgens - androgens bring about the development of the male internal sex organs - the development of the female sex organs do not need to be stimulated by a hormone - the fetal stage: begins with the appearance of bone cells and ends with birth. At the end of the 2 month of pregnancy, fetus is 4 cm and weighs 30 g rd - at the end of the 3 month, major organs have developed - at the end of the 4 month, fetus is about 15 cm and weighs 170 g - if fetus is born prematurely at 7 months, it has a good chance at survival threats to normal prenatal development - most important factor in the fetus development is the mothers diet - if the mother is malnourished, the fetus’s nervous system develops abnormally, and intellectual deficits may result - teratogens can also cause birth defects - certain antibiotics when taken over long periods of time can cause birth defects - tetracycline, a common antibiotic can cause irregularities in the bones and discoloration of the teeth - if a pregnant women uses cocaine, theres an increased risk of premature birth, low birth weight and smaller then normal head circumference - cigarette smoking can also affect the fetus - reduced oxygen levels are especially important during the last half of pregnancy when the fetus is developing most rapidly - maternal smoking is associated with deficits in the ability of a newborn babys brain to process speech sounds motor development - maturation: refers to any relatively stable change in thought, behavior or physical growth that is due to the aging process and not to experience. - at birth, the infants most important movements are reflexes- automatic response movements - development of motor skills requires 2 things: - maturation of a child’s nervous system and practice - physical development of the nervous system depends a lot on the ways in which the baby moves while interacting with the environment adolescence - there are no distinct physical changes that mark the transition from adolescence into adulthood - puberty- the period when people’s reproductive systems mature - the internal sex organs and genetalia don’t change until puberty - when boys and girls reach about 11-14, their testes or ovaries secrete hormones that begin the process of sexual maturation - this activity of the gonads is initiated by the hypothalamus - the hypothalamus instructs the pituitary gland to secrete hormones that stimulate the gonads to secrete sex hormones - these hormones cause the maturation of ova and the production of sperm (considered primary sexual characteristics b/c they are essential to the body to reproduce) - estradiol causes womens breasts to grow and their pelvis to widen and it produces changes the layer of fat beneath the skin - first menstrual period begins at around age 12 - in boys, first visible event of puberty is the growth of the testes and scrotum followed by appearance of pubic hair - sexual maturity- the ability to father a child occurs at around age 15 behavioural effects of puberty: - most adolescents display a form of egocentrism that develops early in the transition into the stage of formal operations: self-consciousness - early maturing boys tend to be more socially mature and perceived as leaders by their peers - later maturing boys tend to become hostile and withdrawn Week 16: Chapter 12: pg. 369-377 and 390-391 Work of jean piaget - jean piaget viewed cognitive development as a maturational process. - Important component of Piaget’s theory is the notion of operation - Operation: in piaget’s theory, a logical or mathematical rule that transforms an object or concept into something else - Important logical characteristic of an operation is that it is invertible- it can be reversed - Important aspect of cognitive development is whether a child possesses the ability to use operations of different types - As children develop, they aquire mental representations that are used for understanding and dealing with the world - Schema: a mental framework that organizes and synthesizes information about a person, place or thing - Schemata are first defined in terms of objects and actions but that later they become the basis of the concrete and abstract concepts that constitute adult knowledge - 2 processes help a child adapt to his or her environement: 1. assimilation: the process by which new information is incorporated into existing schemata 2. accommodation: the process by which existing schemata are changed by new experiences - at key points in an individuals life, the 2 processes (assimilation and adaptation) fail to adjust adequately. At these points, Piaget labeled it equilibrium- the individuals schemas are radically reorganized. - These key points are divided into 4 periods: 1. Sensorimotor 2. Preoperational 3. Concrete operational 4. Formal operational - What a child learns in one period, enables him or her to progress to the next period Sensorimotor period - Lasts for first 2 years of life - Marked by an orderly progression of increasingly complex cognitive development ranging from reflexes to symbolic thinking. - Object permeanence: the idea that objects don’t disappear when they are out of sight - Cognition is inseperable from action or behavior- thinking is doing - Last half of the first year, infants can grasp objects, turn them over, and investigate their properties - During this last half of the first year, out of sight is no longer out of mind. If an object is hidden, it still exists - In the 2 year, infants will search for an object in the last place they saw it hidden. Infants can keep track of changes in a hiding place that they can see Preoperational period - Lasts from ages 2-7 and involves the ability to think logically as well as symbolically - Period is characterized by rapid development of language ability and of the ability to represent things symbolically - Schema
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