Temperature Regulation When studying temperature regulation the body can be divided into two...
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Transcript of Temperature Regulation When studying temperature regulation the body can be divided into two...
![Page 1: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/1.jpg)
Temperature Regulation• When studying temperature
regulation the body can be divided into two regions: the core and the shell.
• Core (internal organs)– temperature highly regulated (high
gain)– traditional values: 37°C, 98.6°F 1°F within normal range– small variations with time of day,
exercise and environmental temperature
Fig. 14-22 G
![Page 2: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/2.jpg)
• Shell (skin and limbs)– temperature not highly
regulated (low gain)– varies with changes in
environmental temperature
• Cold Environment– body heat conserved for the
core– shell allowed to become cold
• Warm environment– excess heat leaves body via
the shell
Fig. 14-21 G
![Page 3: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/3.jpg)
Physics of Heat
• heat = molecular motion– cold = absence of heat
• downhill movement– from region of higher temperature
to region of lower temperature
• Flow of heat = temperature gradientX conductance
![Page 4: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/4.jpg)
Mechanisms of Heat Transfer
1) Radiation, especially infrared2) Conduction: heat transfer by direct contact
conductors – high conductanceinsulators – low conductance (high resistance)
Convection: conduction due to movement of a liquid or gas
From Guyton,Medical Physiology
![Page 5: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/5.jpg)
Mechanisms of Heat Transfer
3) Evaporation
– 0.58 Cal required to evaporate 1g of H2O from the surface of the skin.
heat of vaporization = 0.54 Cal
1 Cal = 1 kcal1 Cal (“nutritional” calorie) = 1000 cal (“physics” calorie)
– When environmental temperature > body temperature, evaporation is the only mechanism to cool the body.
![Page 6: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/6.jpg)
Roles of the Skin
insulation
Fig. 6.1
evaporative cooling
vasodilation and vasoconstriction
![Page 7: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/7.jpg)
Roles of the SkinRadiationConductionConvection
Modulated by vasodilation and vasoconstriction
From Guyton,Medical Physiology
![Page 8: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/8.jpg)
Roles of the Skin
evaporative cooling
maximum rate of perspiration= 2-3 L H2O/hr
Na+, Cl-, K+, urea, and lactic acidare also excreted in sweat.
Fig. 6.1
![Page 9: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/9.jpg)
Central Control of Body Temperature
• Controlled Variable– temperature of body core
• Set Point– 37oC
• Receptors– central thermoreceptors: in hypothalamus of brain – peripheral thermoreceptors: in skin (mostly affect
behavior, very little role in regulating core temperature)• Control Center
– hypothalamus• Effectors
– dermal blood vessels– skeletal muscle– endocrine glands – brown fat– sweat glands
![Page 10: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/10.jpg)
Hypothalamic Control of Body Temperature
When core body temperature drops below the set point, the following mechanisms are activated to increase body temperature:
heat loss vasoconstriction [piloerection] heat production shivering
muscle contraction generates heat
hormone secretione.g., thyroxine, epinephrine (adrenaline)
activation of brown fate.g., in human infants mitochondria generate heat instead of ATP
![Page 11: Temperature Regulation When studying temperature regulation the body can be divided into two regions: the core and the shell. Core (internal organs) –temperature.](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649da15503460f94a8cb49/html5/thumbnails/11.jpg)
Hypothalamic Control of Body Temperature
When core body temperature rises above the set point, the following mechanisms are activated to decrease body temperature:
heat loss vasodilation (inhibit vasoconstriction) sweating
heat production voluntary activity fuel intake thyroxine secretion