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PSYC 100
Ingrid Johnsrude

WEEK 15 ONLINE LESSON NOTES: LIFESPAN DEVELOPMENT human development: before birth-->death GERMINAL PERIOD -first stage of development; when a sperm cell fuses with an ovum (zygote, diploid) -during this period, zygote divides many times through cleavage (24 hours after conception) -resulting cells held together in a sphere (morula) -conception in fallopian tubes, travels until it enters uterus -lasts until developing cells have attached to uterine wall (8-10 days after conception) -sperm and ovum--> gametes, haploid (1/2 the chromosomes of a human) Epigenetic modification: even though all the DNA of our cells are identical (except gamete cells), they are expressed differently--> different genes on/off, different expression of proteins and cell f'n Stem cells: cells w/ the same DNA as every other cell, but have not undergone epigenetic mod. -can become any type of cell (eg. cells of morula) -flexible in their development: any morula cell can potentially become the fetus (eg. identical twins) EMBRYONIC PERIOD -as morula enters uterus, uterus fills with fluid -hundreds of cells, now -cells begin to differentiate into 2 layers: inner mass: develops into embryo trophoblast: forms a surrounding layer, protecting inner mass and sending nutrients to it -develops into extra-embryonic tissue (eg. placenta-->exchange of O2 and metabolites b/w mom and embryo) -amniotic sac: embryo develops in it -placenta: attaches to inside of amniotic sac and umbilical cord of embryo -filter, protective barrier -prevents and chemical blood of child and mom from mixing, eliminates child's waste , etc. -differentiation: morula --> blastocyst -lasts approx. 8 weeks -embryo separate into: -endoderm: innermost layer of tissue (digestive system, urinary tract, lungs) -mesoderm: middle layer (muscle, bone, circulatory system) -ectoderm: outer layer (skin, hair, teeth, CNS); layer rolls into the inside, forms a small tube of ectoderm inside the embryo w/ some ectoderm covering the outside (CNS inside child)--> neural tube(brain and spinal cord) through neurulation, after 3 layers diff. -neurogenesis: growth of neurons, cells that make up CNS develop inside neural tube, 6-7 weeks after conception; peak period of neuron growth NEURAL MIGRATION -neurons organize themselves spontaneously, in an appropriate pattern; factors: -genetics act as blueprint for pattern -timing and location of neurogenesis -interaction w/ glial cells -combo of genetic, environmental, and chem signals -during embryonic period, heart will form and pump blood -begin to develop most organs and limbs -begins to respond in a limited way to stimuli [email protected] end of period, gonads develop and sexual differentiation begins -embryonic period proceeds according to: 1. Cephalocaudal: development occurs most intensely @ head, moves down body 2. Proxiodistal: proceeding from centre, moving outwards BODY TRIMMING -apoptosis: cell death will be genetically programmed to occur to define things (eg. flipper-- >fingers, removes webbing) FETAL PERIOD -final period of prenatal development; 9 weeks - birth -breathing motions/muscle contractions, sleep/wake patterns emerge, movement that mom can detect, vestibular system develops, responsive to sound, recognizes mom's voice -6 months: can survive premature birth -reacts to light stimulation, spontaneous movement decreases, tastes STRESS + NUTRITION Stress -premature delivery and low birth weight (leads to reduced growth, more respiratory problems, lower cognitive ability), anxiousness/depression, and increased aggression of child after birth Good Nutrition -aids in typical brain development and prevention of some birth defects Malnutrition -underweight babies, small heads, serious physical malformations, higher rates of illness Teratogens -external compounds that cause extreme deviations from typical development if introduced to a developing organism (eg. heavy metals, some medications, alcohol) -susceptibility of developing organism to teratogen depends on when it faced exposure -timing of exposure affects which part of the body is affected -depending on the mom + fetus, the degree of the affects will vary -amount and length of exposure influences effects on fetus -greater the amount and/or length of exposure, more drastic the effects on the fetus Alcohol -crosses the placenta, enters the amniotic fluid that the fetus consumes -Fetal Alcohol Spectrum DIsorder (FASD): most common cause of mental retardation -->ranges from subtle abnormal behavior to sever facial deformities, attentional disorders, mental retardation, congenital heart disease, and hyperactivity Tobacco -nicotine causes abnormal development of the placenta(nourishes fetus, filters O2, protection) -babies weight less, more at risk at Sudden Infant Death Syndrome, lower IQ, and behavioral problems Prescription Drugs -some drugs can cause birth defects Diseases -some diseases can cross the placental barrier -eg. Rubella: if contracted within first 3 months--> congenital heart disease, deafness, blindness, mental retardation -eg. Influenza: caught during early to mid-pregnancy--> correlated to schizo later in life CONFOUNDS + LARGE POP'NS -factors affecting prenatal development hard to control in large human pop'ns and not always replicable -eg. famine also comes with stress, and increases susceptibility to illness--> hard to isolate the factor that affected development in a certain way -lots of confounding variables -besides confounds, many uncontrollable factors can contribute to development -studies are hard to replicate to reinforce findings (eg. would have to wait for another famine) -conducting experiments to see what affects prenatal development: --> not ethically sound to impose conditions; must do correlation studies -->lots of variables to keep track of (eg. amount of smoke, time smoking, etc) -->lots of external confounding variables (stress, genetics, etc.) -->determining cause and effect is difficult -hard to perform high-quality research on large human pop'ns CHILDHOOD DEVELOPMENT -newborns are born with some behaviors already in place -reflexes: specific complex actions that occur automatically in response to certain stimuli -eg. rooting reflex: cheek touch--> babies turn their heads towards it and open their mouth -for feeding -eg. sucking reflex: baby will suck on anything that enters its mouth -eg. babinsky reflex: foot stroked--> fan and curl toes -eg. tonic neck reflex: head to one side, extend arm on same side of gaze, flex arm/knee on opposite side -eg. moro reflex: babies throw out arms and grasp if they feel themselves dropping unexpectedly -grasping reflex: birth-3 months; automatically close their hands on anything against their palms -pre-reaching: poorly guided, ineffective arm movements towards interesting visual stimuli [email protected] 3 months, replaced by voluntary grasping -more accurate arm movements and visual feedback--> associated w/ maturation of visual and motor cortices in brain + stronger muscles in neck, shoulders, and arms
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