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Thermoregulation in animals
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Animals live in a relatively narrow range of body temperatures
Temperature affects most physiological processes (Q10 = 2-3) Physiological processes (and enzymes) often exhibit optimal response curves;
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A cold-blooded animal (poikilotherm) is one whose internal temperature varies along with that of the ambient environmental temperature.
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a warm-blooded (or homeothermic) animal keeps its body temperature at a roughly constant level, regardless of the ambient temperature.
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Endothermy is the ability of some creatures to control their body temperatures through internal means such as muscle shivering or fat burning. Ectothermic refers to organisms that control body temperature through external means.
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Ectotherms organisms that control body temperature through external means.
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Terminology Cold blooded vs. warm-blooded - rarely used often inaccurate, misleading, and biologically uninformative Poikilothermic (variable Tb) vs. homeothermic (constant Tb) Ectothermic (environmental heat gain) vs. endothermic (physiological heat gain); preferred - focus on processes rather than results Limitations of all terminology (large physiological diversity; not all organisms can be conveniently categorized); e.g., some insects, birds, and mammals routinely generate heat by physiological processes but also bask to gain environmental heat)
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Regulation of Body Temperature: Energy Balance in the Body
Figure 22-18
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Thermoregulation in endotherms
benefits: independent of Te, specialized cellular function, high aerobic capacity costs: very high energetic cost (90% assimilated)
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Regulation of Body Temperature: Heat Balance in the Body
Body temperature is a balance between heat production, gain, and loss Figure 22-19
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importance of shell/core concept
Maintenance of Tb range requires heat transfer between body and environment Tb not uniform throughout body;
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counter-current heat exchange
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Thermal receptors and thermoregulatory centre
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Regulation of Body Temperature: Thermoregulatory Reflexes
Figure (1 of 2)
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Regulation of Body Temperature: Thermoregulatory Reflexes
Figure (2 of 2)
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Regulation of Body Temperature
Alterations in cutaneous blood flow conserve or release heat Sweat contributes to heat loss
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Panting increases heat loss
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Heat production Voluntary muscle contraction and normal, metabolic pathways Regulated heat production Shivering versus nonshivering thermogenesis# # Brown fat--especially abundant in newborns and in hibernating mammals. It generates body heat in animals or newborns that do not shiver
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Regulation of Body Temperature
Homeostatic responses to environmental extremes Figure (1 of 2)
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Regulation of Body Temperature
Figure (2 of 2)
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Regulation of Body Temperature
Body’s thermostat can be reset Pathological conditions Hyperthermia Heat stroke Hypothermia
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Frostbite True freezing injury of tissues.
Onset signaled by sudden blanching of the skin of nose, ears, cheeks, toes, followed by tingling. Frostbite has declared itself when these areas are painless. Intense coldness followed by numbness.
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Dressing for the C O L D Keep Clothing Clean Avoid Overheating
Dirt and grease block up the air spaces in your clothing and reduce the insulation value. Avoid Overheating Sweat can freeze on outer layers. Stay dry, moisture will decrease the insulating ability of your clothing. Wear Clothing in Layers Loose clothing allows air spaces to help trap warm air without restricting blood circulation. Good blood circulation helps to prevent frostbite. Keep Clothing Dry You’ve got to keep your clothing dry, from the outside as well as from the inside.
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Desert vs Arctic fox
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large animals use more total energy than smaller animals
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small animals have higher energy demands than large animals measured per unit mass
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