thermoregulation n.
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Thermoregulation. Homeostasis. Homeostasis. organ systems are interdependent share same environment c omposition effects all inhabitants internal environment must be kept stable maintaining stable internal environments-homeostasis dynamic equilibrium. Homeostasis.

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  • organ systems are interdependent
  • share same environment
  • composition effects all inhabitants
  • internal environment must be kept stable
  • maintaining stable internal environments-homeostasis
    • dynamic equilibrium
  • varies around a Set Point
    • average value for a variable
  • specific for each individual
    • determined by genetics
  • normal ranges for a species
    • temperature 36.7 – 37.2
parts of homeostatic regulation
Parts of Homeostatic Regulation
  • Receptor
    • sensitive to environmental change or stimuli
  • Control or Integration Center
    • receives & processes information supplied by receptor
    • determines set point
  • Effector
    • cell or organ which responds to commands of control center
homeostatic regulation
  • Autoregulation
    • cells, tissues, organs adjust automatically to environmental changes
  • Extrinsic Regulation
    • Nervous System
      • Fast
      • Short lasting
      • Crisis management
    • Endocrine System
      • Longer to react
      • Longer lasting
feedback loops
  • Negative Feedback
    • output of system shuts off or reduces intensity of initiating stimulus
    • most often seen in the body
  • Positive Feedback
    • initial stimulus produces a response that exaggerates or enhances its effect
    • blood clotting & child birth
temperature extremes
Temperature Extremes
  • Humans are subjected to vast changes in environmental temperatures
  • Enzymes operate over very narrow range of temperatures
  • Failure to control body temperature can result in physiological changes & damage
  • body has several mechanisms to maintain body temperature
  • Thermoregulation
  • Core temperature
    • most important body temperature
    • temperature of organs in major cavities
    • rectal temperature gives best estimation
  • Shell temperature
    • temperature closer to surface
    • skin & oral temperatures
mechanisms of heat transfer
Mechanisms of Heat Transfer
  • Radiation
  • Conduction
  • Convection
  • Evaporation
  • water changes from liquid to vapor
thermoregulation homeostasis
  • Control Center
    • preoptic area of hypothalamus
  • Receptors
    • in skin
  • Effectors
    • eccrine sweat glands & blood vessels
mechanisms for heat loss
skin receptors detect increase in temperaturemessage sent to preoptic nucleus heat loss center (also in hypothalamus)stimulated sets off series of events heat loss

inhibition of vasomotor centerperipheral vasodilationwarm blood flows to skin’s surface

as skin temperatures rise, radiation & convection loses increase

sweatglands stimulated increase output evaporative loss increases

respiratory centers stimulateddepth of respiration increases

Mechanisms for HeatLoss
mechanisms for heat gain
Mechanisms for Heat Gain
  • skin receptors notice temperature is droppingpreoptic nucleus notificed
  • heat loss center inhibited
  • heat gain center activated
  • sympathetic vasomotor center decreases blood flow to dermis of skin
  • vasoconstriction reduces heat loss by radiation, convection & conduction
  • blood returning from limbs is shunted into deep veins
  • Piloerector muscles are stimulatedhair stands on endtraps air near the skin
heat gain
Heat Gain
  • if vasoconstriction cannot restore or maintain core temperatureshivering thermogenesis begins
    • gradual increase in muscle tone
    • increases energy consumption by skeletal muscle throughout body
    • increases work load of muscles & elevates O2 & energy consumptionproduces heat which warms deep vessels to which blood has been shunted by sympathetic vasomotor center
  • can increase rate of heat generation by


heat gain1
Heat Gain
  • Non shivering thermogenesis
    • long term mechanism for heat production
  • sympathetic nervous system & thyroid hormone produce an increase in metabolism
  • Heat gain center stimulates adrenal medulla via sympathetic ANSepinephrine released increases rate of glycogenolysis (break down of glycogen) in liver & skeletal musclemetabolic rate increases
  • preoptic nucleus regulates production of TRH-thyrotropin releasing hormone by the hypothalamus
  • TRH increases production of thyroxin by thyroid gland
  • Thyroxin is a key hormone in control of metabolism