Thermoregulation
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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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Thermoregulation

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Thermoregulation

Thermoregulation

Homeostasis


Homeostasis

Homeostasis

  • organ systems are interdependent

  • share same environment

  • composition effects all inhabitants

  • internal environment must be kept stable

  • maintaining stable internal environments-homeostasis

    • dynamic equilibrium


Homeostasis1

Homeostasis

  • 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

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

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


Negative feedback

Negative Feedback


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


Temperature

Temperature

  • 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


Evaporation

Evaporation

  • water changes from liquid to vapor


Thermoregulation homeostasis

ThermoregulationHomeostasis

  • 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

    400%


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


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