rav65819_ch50_1017-1038

rav65819_ch50_1017-1038 - ; 50 chapter Temperature, Osmotic...

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Temperature, Osmotic Regulation, and the Urinary System concept outline 50.1 Regulating Body Temperature Q 10 is a measure of temperature sensitivity Temperature is determined by internal and external factors Organisms are classiFed based on heat source Ectotherms regulate temperature using behavior Endotherms create internal metabolic heat for conservation or dissipation Mammalian thermoregulation is controlled by the hypothalamus 50.2 Osmolarity and Osmotic Balance Osmotic pressure is a measure of concentration difference Osmoconformers live in marine environments Osmoregulators control their osmolarity internally 50.3 Osmoregulatory Organs Invertebrates make use of specialized cells and tubules Insects have a unique osmoregulatory system The vertebrate kidney Flters and then reabsorbs 50.4 Evolution of the Vertebrate Kidney ±reshwater Fshes must retain electrolytes and keep water out Marine bony Fshes must excrete electrolytes and keep water in Cartilaginous Fshes pump out electrolytes and retain urea Amphibians and reptiles have osmotic adaptations to their environments Mammals and birds are able to excrete concentrated urine and retain water 50.5 Nitrogenous Wastes: Ammonia, Urea, and Uric Acid Ammonia is toxic and must be quickly removed
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Urea and uric acid are less toxic but have different solubilities 50.6 The Mammalian Kidney The nephron is the Fltering unit of the kidney Water, some nutrients, and some ions are reabsorbed; other molecules are secreted Excretion of toxins and excess ions maintains homeostasis Each part of the mammalian nephron performs a speciFc transport function 50.7 Hormonal Control of Osmoregulatory Functions Antidiuretic hormone causes water to be conserved Aldosterone and atrial natriuretic hormone control sodium ion concentration ON A COLD WINTER DAY, the temperature in many regions will be near freezing. Yet when you leave your house, your core body temperature will not immediately drop. The reason is that you are producing heat internally, and you have a thermostat in your brain with a temperature set point. In addition, the majority of your body weight is actually water, and you exist in a very dehydrating environment by comparison. You are able to do this because of elaborate mechanisms that allow you to retain water and to control the osmotic strength of your blood and extracellular fluids. Both the regulation of internal temperature and the regulation of internal fluid and its composition are examples of homeostasis— the ability of living organisms to maintain internal conditions within an optimal range. In this chapter, we discuss these two kinds of regulation. Animals exhibit a number of adaptations to help regulate temperature, including behavior such as that of the elephant pictured. We also describe the osmoregulatory systems of a number of animals, including the mammalian urinary system. These organ
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This note was uploaded on 10/15/2010 for the course BIO BIO1 taught by Professor Lipke during the Fall '09 term at CUNY Brooklyn.

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rav65819_ch50_1017-1038 - ; 50 chapter Temperature, Osmotic...

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