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Temperature Regulation

Temperature Regulation. Maintaining Homeostasis with the Environment. Principles of Heat Balance. 2 nd Law of Thermodynamics: heat moves from a warmer body (heat source) to a colder body (heat sink)

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Temperature Regulation

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  1. Temperature Regulation Maintaining Homeostasis with the Environment

  2. Principles of Heat Balance • 2nd Law of Thermodynamics: heat moves from a warmer body (heat source) to a colder body (heat sink) • Enzymes usually only work with in 10 degrees Celsius temperature range before they lose their conformation (denature). • Heating: • Conduction:  The movement of heat • Convection: The movement of air or water in currents (rise as they warm) • Radiation: Transfer of energy in electromagnetic waves • Evaporation:  gives off excess heat

  3. Body size and the transfer of heat • Transfer of heat is proportional to body surface exposed (surface area) • Small animals "huddle" Emperor penguin huddle Birds huddle on a wire

  4. "Cold-Blooded" –vs- "Warm Blooded" : "thermoregulation" • Ectotherm- "changeable" body temperature • Mostly aquatic - large bodies of H2O vary very little in temp.  • “Cold-blooded"; aka POIKILOTHERMS • They cannot control their own internal body temperature, but they are rarely actually "cold" and have other means to thermoregulate: • Snakes and lizards sunning themselves on rocks; “basking” • Fish changing depths in the water column to find a suitable temperature. • Desert animals burrowing beneath the sand during the day. • Insects that warm their flight muscles by vibrating them in place. • Dilating or constricting peripheral blood vessels to adapt more or less quickly to the ambient temperature.

  5. "Cold-Blooded" –vs- "Warm Blooded" : "thermoregulation" • Endotherm- able to maintain a constant body temp. • Land changes temp. rapidly, animals must adjust quickly. • “Warm-blooded"; aka HOMEOTHERMS • Metabolic heat (from glucose oxidation)= high energy expenditure • Warmer at center (organs) • The "Q10 effect":  the multiple by which a particular enzymatic reaction or metabolic process increases with each ten-degree Celsius increase in body temp.

  6. The Thermostat • The Hypothalamus: interprets information from thermoreceptors throughout the body. • Releases thyrotropin-releasing hormone (TRH) in response, which triggers the pituitary… • Pituitary Gland • Releases thyroid-stimulating hormone (TSH), which affects the thyroid… • Thyroid Gland • Releases Thyroxine (metabolic rate increases = temperature (body heat will then increase).

  7. Regulatory Strategies: • Regulating Falling Body Temp : • Blood vessels near skin constrict (to limit heat loss) • Metabolism speeds up • Shivering • Hair stands up (erector muscles in skin) to trap warm air Regulating Rising Body Temp : • Expose more body surface (heat loss) • Evaporation from skin surface (perspiration) • Panting • Blood vessels in skin dilate (to release heat into environ.)

  8. Cutting energy losses • Diurnal- vs- nocturnal • Hibernation – Slow down HR, metabolism, breathing, etc. but constantly monitor external environment • Fat Insulation- Seals • Fat Localization- Camels

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