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Thermoregulation. “The maintenance of a particular temperature of the living body” –Mariam-Webster Ideal temperature Regulation Hypothalamus Hypothermia Hyperthermia Thermogenesis. The Merck Veterinary Manual. Regulation. External heat transfer mechanisms

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thermoregulation
Thermoregulation
  • “The maintenance of a particular temperature of the living body” –Mariam-Webster
  • Ideal temperature
  • Regulation
  • Hypothalamus
  • Hypothermia
  • Hyperthermia
  • Thermogenesis
regulation
Regulation
  • External heat transfer mechanisms
    • Radiation-emission of infrared radiation
    • Conduction-transferring through physical contact
    • Convection-transfer by movement of liquid or gas between areas of different temperature
    • Evaporation-conversion of liquid to vapor
  • Regulated by neural feedback mechanisms that operate through the hypothalamus primarily
  • Hypothalamus contains control mechanisms & key temperature sensors
hypothalamus
Hypothalamus
  • Group of neurons in anterior portion- preoptic area
  • As temperature rises neurons increase activity
  • As temperature drops neurons decrease activity
  • Nerve impulses of the preoptic area work with heat-loosing and heat-promoting centers of the hypothalamus
hyp o thermia
Hypothermia
  • Animals can have low temperatures after birth due to dystocia and being hypoxic
  • Feed warm colostrum
  • Can partially compromise the immune system
  • Newborn has a poorly developed ability to shiver
  • Low volume but high surface area for the heat to escape
hypothermia
Hypothermia
  • Responses initiated to save body heat and increase heat production
    • Vasoconstriction to decrease the flow of heat to the skin
    • Cessation of sweating
    • Shivering to increase heat production in the muscles
    • Secretion of norepinephrine, epinephrine and thyroxine to increase heat production by increasing the BMR
    • Raising of hairs to increase insulation
    • Production of thyroid hormones that initiate burning of food
      • Thyroid hormones regulate BMR
hyperthermia
Hyperthermia
  • Fat layer-can be thin in newborns
  • Arterioles dilate to move heat out through the skin
  • Sweating
  • The mother keeps the fetus warm
    • Fetus and placenta have such a high metabolic rate that the fetus is ~.5⁰C warmer than the mother (Orville, 2014)
thermogenesis
Thermogenesis
  • “The production of heat especially in the body (as by oxidation)” –Mariam-Webster
  • Brown Adipose Tissue
  • Born with most at birth
    • Usually 2-4% of birth weight (Symonds, 2013)
    • Thermogenic capacity is at peak at birth
  • Adult’s amount increases with exposed to cold & decreases with age and BMI
  • In lower neck/chest
    • In lumps like glands
thermogenesis1
Thermogenesis
  • Functions to distribute stored energy as heat
    • Large number of mitochondria-produce ATP
    • Produced through activation of uncoupling protein 1 (UCP1)
    • Can produce up to 300 watts/kg of heat
      • All other tissue can only produce up to 1 watt/kg
  • Pigs lack brown adipose tissue
    • Nonfunctional UCP1 gene
    • Dependent on shivering thermogenesis

(Symonds 2013)

thermogenesis2
Thermogenesis
  • Non-Shivering Thermogenesis
  • Cold exposure causes sympathetic stimulation of brown adipocytes by norepinephrine binding to beta-adrenergnic receptors
  • In brown adipocytes, most fatty acids are directly oxidized and a large amount of heat is produced
  • In white fat, sympathetic stimulation causes hydrolysis of triglycerides
    • Release of glycerol and fatty acids
    • More for insulation than heat production
thermoregulation1
Thermoregulation
  • PGC1α-master regulator of mitochondrial biogenesis in many species
    • Required to heat production of BAT
  • By decreasing thyroid hormones in the plasma by blocking the secretion or being in a warm environment leads to a loss of UCP1 and enhances the breakdown of white adipose tissue
    • Hypothyroidism as a newborn leads to impaired thermoregulation and sometimes death

(Symonds, 2013)

4 stages of adipose tissue development in early life
4 Stages of Adipose Tissue Development in Early Life

Summary of the main developmental changes in adipose tissue during early life.

(Symonds, 2013)