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Lecture 5

HLTB02H3 LECTURE 5 notes.docx

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Health Studies
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HLTB02 – LECTURE FIVE = ENVIRONMENTAL FACTORS Determinants of Human Growth:  Genetic  Endocrine system  Cultural factors  Environmental factors Environment Bergman‘s Rule: populations in colder climates are fenerally larger, with wider torsos/stockier stature, since reduced surface area relative to body weight limits heat loss Allen‘s Rule: populations in colder climates will have shorter arms and legs relative to height (to limit heat loss), while those in warmer climates will have longer arms/legs Note: improved nutrition, particularly in tropical regions, is now reflected in weaker climate-body size relationships than in past Environment:  Temp o Cold – requires higher rate of basal metabolic rate and robs body of energy used for growth  Energy used to keep body alive instead of growth  Altitude o Reduced oxygen  hypoxia, high solar radiation, cold, low humidity, high wings, rough terrain  Limits life and agricultural productivity o Hypoxia: most severe climatic stress  Less oxygen reach body tissues, can‘t be compensated by cultural or behavioural adaptions  Normal RBC saturated with oxygen 97%, at 3000 m, 90% only  Enough to disrupt cellular growth and metabolism  Ex. lower birth weight, Bolivia = 3.1 kg vs. 3.4 kg o Hypoxia + poor nutrition (synergy – must be together to have worse effect than either individually) = shorter lighter kids, reduced rate of growth  Other studies suggest the ooposite: better growth rates in high altitude vs. low altitude kids in same region  Poorer health and nutrition ‗cause malaria and parasites in lower altitudes (moist, warm, humid)  Seasonality o Temperate latitudes – climate can affect growth (spring births vs. fall births – could be sunlight)  Could act on human endocrine system directly, synchronize body‘s natural fluctuations in growth regulating hormone activity o Height: vitamin D, increases intestinal absortion of Ca and controls the rate of skeletal remodeling and mineralization of new bone  Hypothalamus releases hormones that stimulate/inhibit release of pituitary hormones  Pituitary gland releases hormones into circulation moving to specific target tissues  Thyroid hormones = thyroxin, triiodothyronine  Gonadal hormones = luteinizing hormone, follicle-stimulating hormone]  Adrenal hormones from kidneys = glucorticoids, ex. cortisol and androgens  Growth hormone from liver o Weight: can be product of food availability (seasonal food shortages)  Pollutants: o Natural and anthropogenic  Anthropogenic:  Air o Smoke – cooking, fire, coal-burning respiratory diseases, lung cancer, cigarettes  Second-hand smoke, during pregnancy  lower birth weight, altered fetal growth but continued exposure => respiratory conditions, Sudden Infant Death Syndrome (SIDS), ADHD, depression, cognitive impairment, later adult health problems, cancer o Smog – burning of fossil fuels, mixed with fog: photochemical smog – action of sunlight on chemicals found in air pollution (car exhaust) o Industrialization chemicals – CO, nitrogen oxides, asbestos, etc.  Water pollution – contamination from landfills and waste water from industrial plants; natural disasters and hurricanes o Chemical fertilizers, seepage down to water table, leaching from plant, to soil to earth to layers to water reservoirs and shit o Health effects: leukemia, cancer, neurological disorders  Solid Waste Pollution o leads to air and water – burned shit, crap seeps into water  poisoning, respiratory problems, etc.  Ex. Minamata Bay – methylmercury contamination of bay in Japan (aka Minamata disease)  CNS impairment due to severe mercury poisoning o Symptoms: numbness in limbs, muscle weakness, lack of coordination, vision and hearing damage, impaired speech, paralysis, coma and death o Congenital: affected fetuses, showing impairments similar to cerebral infantile paralysis (worse effect that on adults)  Lead Poisoning  Any age affected, children more vulnerable since nervous system
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