Homeostasis

Homeostasis - Homeostasis ! maintenance of physiological...

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Homeostasis 1/28/10 1 Homeostasis ! maintenance of physiological stability in our internal environment. Internal Environment ! blood and lymph – the fluids that surround and bathe our cells. Factors Homeostatically Controlled in Human Blood : Red blood cell concentration Blood pressure Osmotic pressure (H 2 0) pH Chemical concentration of: O 2 , CO 2 , glucose, amino acids, Ca (calcium), P (phosphorus), Na (sodium), K (potassium), Cl (chlorine), Mg (magnesium), Fe (iron), Zn (zinc) Temperature in our body core
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Homeostasis 1/28/10 2 Endotherms ! organisms with physiological temperature control – their temperature is generally higher than the environment. = “warm-blooded,” e.g. birds and mammals Ectotherms ! organisms without significant physiological temperature control – they use mostly behavioral mechanisms to control their temperature = “cold-blooded,” e.g. fish, amphibians, reptiles, molluscs, arthropods, etc. Endothermy roughly equals warm-bloodedness
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Homeostasis 1/28/10 3 ENDOTHERMY Advantages : A. Higher activity levels " faster response times B. Fewer ecological restrictions " 1. Active at night as well as daytime 2. Active in the winter as well as summer 3. Active in the arctic as well as the tropics Disadvantages: A. High energy demands ( i.e., food intake) " B. High oxygen demands
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Homeostasis 1/28/10 4 Factors Affecting Body Temperature The body’s ratio of surface area relative to its overall volume (S/V). Heat escapes the body only through its surface. Cardiovascular adaptations Presence or absence of good insulation Evaporative cooling mechanisms Behavior mechanisms Body metabolism is the organism’s internal furnace Body thermostat in the hypothalamus of the brain controls the organism’s body core temperature
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Homeostasis 1/28/10 5 Surface-to-Volume Ratios (S/V) in Endotherms S/V # to appendage length (a function of body shape) # to 1 /size = 1 /x, where x = a linear dimension (a function of body size). Smaller endotherms have a greater S/V than large ones # to metabolic rate or heart rate (small endotherms need to be more active because they lose heat much more quickly) # to 1 /life span of the individual. Smaller, more active endotherms tend to wear out more quickly.
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Homeostasis 1/28/10 6 Surface/Volume # x 2 /x 3 # 1 /x # 1 /size (where “x” is a linear dimension) cm S = 1x1x6 = 6 surface units = 6 cm 2 V = 1x1x1 = 1 volume unit = 1 cm 3 S/V = 6/1 = 6 cm 2 / 1 cm 3 S = 2x2x6 = 24 surface units = 24 cm 2 V= 2x2x2 = 8 volume units = 8 cm 3 S/V = 3/1 = 3 cm 2 / 1 cm 3 S = 8x8x6 = 384 cm 2 V = 8x8x8 = 512 cm 3 S/V = 3 cm 2 / 4 cm 3 = ! of a surface unit for each volume unit
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This note was uploaded on 01/31/2010 for the course EBIO 1050 taught by Professor Basey,john during the Summer '08 term at Colorado.

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Homeostasis - Homeostasis ! maintenance of physiological...

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