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PSY100H1 (1,831)

Ch 5 Txt Notes + Obesity Article.docx

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Michael Inzlicht

CHAPTER 5: GENETICS AND THE DEV OF THE HUMAN BRAIN Genetics and Behv Disorders of Brain Dev Neural Tube Defects • Anencephaly: o Rostral neural tube does not develop properly o majority die in utero or do not survive for more than a few hours after birth • Spinal Bifida o Caudal neural tube fails to close normally o Live w/ Surgery within 24 hrs after birth can correct  Nonetheless, most develop lower limb paralysis • Neural tube defects may be caused by folic acid deficiencies o Dark green leafy vegetables, fruits, juices, egg yolks, fortified cereals (nations have done this as a preventative measure) o Avg American diet is insuffifcient o Folic acid fortification  increased risk of colon cancer Genetic Disorders: • Down Syndrome: o Trisomy 21 (3 copies of chromosome 21)  Bc abnormal division/disjunction during meiosis  Related to maternal age o Symptoms: heart deformities, shorter life expectancy, high risk of Alzheimer’s • Fragile-X Syndrome: o FMR-1 gene on the X chromosome normally has 6-50 codon repeats but w/ 200 or more repeats  fragile x o Typical intelligence to moderate retardation o Low-set ears, large forehead and jaw o Males  unusual social withdrawl  Fewer than 5% are actually autistic though • Metabolic disorders: o Body is either unable to produce or overproduces important chemicals o Accounts for 3-7% of severe retardation o Best understood = PKU = phenylketonuria = 1/50 are carriers, but 1/10,000 births o recessive gene for lack of liver enzymes needed to convert amino acid phenylalanine into tyrosine  produce abnormal byproduct = phenylpyruvic acid which damages brain in early dev • can be prevented by avoiding phenylalanine until mid-20s o milk, dairy, meat, fish, chicken, eggs, beans, and nuts Environmental Toxins: • FAS: fetal alcohol syndrome o Mental retardation + growth retardation ( skin folds at corners of eyes, nose and mouth abnormalities, small head circumference, reduced IQ) o More likely to have attention deficits, poor impulse control, severe behv problems o Decreases in grey matter Redev in Response to Damage • Segment of axon that is now separated by the damage area will deteriorate in anterograde (forward) degen • The remaining attached segment regrows sometimes and other times not o Typically, damage very close to cell body  retrograde degen so everything dies • Since all neurons are connected to lots of other ones, when one dies, the others aren’t receiving input from it and so the postsynaptic cells deteriorate by transneuronal degen • Damaged PNS can regrow bc Schwann cells • Oligodendrocytes are not helpful though bc scar tissue inhibits axon regrwoth o Also proteins in growth cones in CNS do not become reactivated but they do in PNS) o CNS damage = generally permanent o But not PNS • Some research in CNS regrowth: o Antibodies to block Nogo = substance that normally prevents further sprouting by mature axons  Nogo inhibitors would promote axon regrowth Adult Nervous System • second wave of gray matter dev + pruning at puberty o cortex thickening peaks at 11 for girls, 12 for boys o followed by gradual thinning  schizo accompanied by 4 times usual thinning o myelination also continues • fully mature by 25 • few changes until about 45 o brain weight decreases o no major cog/behv deficits in healthy yet tho • ppl w/ dementia had watched more TV o compared to those w/ active hobbies + reading • neurons don’t duplicate • but some body cells DO and this is part of aging o at end of each chromosome is a telomere  doesn’t encode any proteins • each tim
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