Body temperature and its regulation
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Transcript of Body temperature and its regulation
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Body temperature and its regulation
S. VasanthanAssistant professor
Department of physiologyMGMCRI
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SLOs• Introduction• Normal temperature• Heat loss mechanism• Heat gain mechanism• Regulation of body temperature• Abnormalities of body temperature
regulation
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IntroductionHomeothermic - maintaining constant internal body
temperature
Endotherms - generate their own internal body heat
Why temperature should maintain?• For normal enzyme activity • For normal neuronal activity • Rise in high temp. cause denature of proteins
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Body temperatureBody temp:
Core temperature measured in oral or rectalSkin temperature measured on skin
Normal body temperature: Oral : 98.6°F (97.3–98.8°F) or 370C (36.3–37.1°C)Rectal : 0.50C more than oral
Axilla : 0.50C less than oral Skin : depends upon the environmentExercise : 101° to 104°F
Rectal 0.50C > oral 0.50C > axilla
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Maintenance of body temp.
Heat loss = Heat gain
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Heat gain mechanism• Shivering• Increase in metabolism by Epinephrine, nor-
epinephrine & thyroxin • Cutaneous Vasoconstriction
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Heat loss mechanism• Evaporation of Sweat• Radiation • Conduction & convection• Cutaneous Vasodilation• Decrease in metabolism• Through respiration
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Regulation of Body Temperature - Role of the Hypothalamus• Receptors: warmth & cold receptors from skin, deep
tissues, spinal cord and hypothalamus
• Heat loss center – Preoptic & Anterior hypothalamic nuclei
• Heat gain center - Posterior hypothalamus
• Set point: 370C in hypothalamus• ± 0.10C cause hypothalamus to activate heat loss or
heat gain mechanism
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Temperature-decreasing mechanismswhen the body is too hot
Vasodilation Sweatingdecrease in thermogenesis (heat production).
Increase in body temperature
Preoptic & Ant. Hypothalamic nuclei
Inhibition of Sympathetic nervous system
Warmth receptors from skin deep viscera are stimulated
Normal body tempSet point: 370C
Posterior hypothalamus
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Temperature-increasing mechanisms when the body is too cold
Skin vasoconstriction throughout the bodyPiloerectionIncrease in thermogenesis (heat production).
Decrease in body temperature
Preoptic & Ant. Hypothalamic nuclei
Posterior hypothalamus
Sympathetic stimulation
Cold receptors from skin are stimulated
Normal body tempSet point: 370C
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Response of hypothalamus
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Abnormalities of body temperature regulation
Hypothermia: decrease in body temp below normal range
Hyperthermia: increase in body temp above normal range
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Hyperthermia - Fever• Increase in body temp above the normal • Due to rise in set point of hypothalamus by
Pyrogen• Pyrogen: any substance that rise the set
point of hypothalamus – Bacterial endotoxins , cell memb proteins &
breakdown products– IL-1– Inflammatory mediators: kinin, bradykinin,
prostaglandin E• Characteristic of febrile condition:
– Crisis– Fever– Crisis or flush
• Antipyretics: aspirin blocks PG-E
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HeatstrokeOccurs when body temp rises beyond the
critical temp ranges from 105 to 1080F
Symptoms:– Dizziness– Abdominal distress,– Vomiting– Delirium– Loss of consciousness– Circulatory shock– Death
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Tepid’s sponging
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Hypothermia
• person exposed to ice water for 20 to 30 minutes ordinarily dies because of heart fibrillation
• the body temperature has fallen below 85°F, the ability of the hypothalamus to regulate temperature is lost
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Frostbite• When the body is exposed to extremely low
temperatures, surface areas can freeze; the freezing is called frostbite.
• especially in the lobes of the ears and in the digits of the hands and feet
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Thank you