RAH_20Lec_2010_20__20Homeostasis - Hough Lecture Outline -...

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Hough Lecture Outline - Homeostasis 1 EVOLUTION OF HOMEOSTASIS: Comparative Physiology of Internal Regulation in Animals [Chapter 49, Raven et al.] Homeostasis: The maintenance of internal physiological conditions in an optimal range within limits of tolerance (a “dynamic constancy”, most importantly conditions such as balance of water, salts, nutrients, gases, wastes, and heat) optimal conditions and tolerance ranges are species-specific homeostasis requires regulation of cell, tissue, or organ function regulation usually involves control systems: Ø sensors – monitor conditions Ø integrating center – compares sensor input to optimal “set point”; signals response action to effectors Ø effectors – cause appropriate change in conditions Ø feedback loop – sensor “informs” integrator when set point is reached [Some loops are negative (e.g. thirst reaction), some are antagonistic (e.g. blood glucose regulation), some are positive (e.g. blood clotting cascade)] DETAILED EXAMPLES: temperature, and water/salt/waste
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Hough Lecture Outline - Homeostasis 2 I. TEMPERATRURE temperature is one of the most basic conditions affecting life: most organisms cannot live below freezing (0 °C, 32 °F) nor above about 45 °C (130 °F), and have optimal ranges much narrower than that temperature influences basic cell and tissue metabolisms rates very directly (as it does all chemical reactions): unregulated metabolic rate doubles or triples for every 10 °C increase in temp. if temp is too low, metabolism stops; if temp is too high, proteins begin to denature (literally “cook”) metabolism itself generates heat, as an entropic product of respiratory oxidation of glucose; animals have varying capacities to conserve and/or amplify this heat in their bodies Categories of temperature relations in organisms: Two heat source categories: ectothermic – body temp controlled by external environmental temp; little or no capability for internal regulation (all organisms except birds and mammals) endothermic – major body heat generated internally, with internal
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This note was uploaded on 08/03/2010 for the course BIO 1500 taught by Professor Pandolfi during the Winter '08 term at Wayne State University.

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RAH_20Lec_2010_20__20Homeostasis - Hough Lecture Outline -...

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