Transcript Temperature Regulation

Temperature Regulation
Maintaining Homeostasis with the
Environment
1
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
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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
3
"Cold-Blooded" –vs- "Warm Blooded" :
"thermoregulation"
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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.
4
"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.
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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).
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Regulatory Strategies:
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.)
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
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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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