Temperature, Osmotic Regulation, and the Urinary System

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Temperature, Osmotic Regulation, and the Urinary
System

• Homeostasis the ability of living organisms to
  maintain internal conditions within an optimal
  range
• a steady-state physiological condition, extremely
  important for the proper functioning of cells

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Homeostasis

• Thermoregulation (temperature)
• Osmoregulation (solute and water balance)
• Excretion (rids system of nitrogen-containing
  metabolic byproducts)

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Thermoregulation

• The rate of any chemical reaction is affected by
  temperature
• The rate of reaction increases with increasing
  temperature
• The rate of reaction decreases with decreasing
  temperature
• Q10 is a quantitative examination of how reaction
  rates vary with temperature

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Thermoregulation, Q10

• Q10 the ratio between the rates of a reaction
  at two temperatures that differ by 10C
• Q10 RT10 / RT

• For example, if Q10 2, then for every 10C
  increase in temperature, the rate of reaction
  doubles (increases by a factor of 2)

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Thermoregulation, Q10

• For most enzymes, Q10 2
• Q10 can also be applied to metabolism (the set of
  all chemical reactions that occur in living
  organisms in order to maintain life)
• In most organisms, the Q10 of metabolism is 2-3
• In some organisms, their Q10 is close to 1
• Little to no change in metabolic rate with
  temperature

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Thermoregulation

• The reactions in your body that make up your
  metabolism are constantly producing heat
• Can be dissipated or used to raise internal body
  temperature
• Metabolic rate and body temperature are
  inter-related
• Lower body temperatures do not permit high
  metabolic rates

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Thermoregulation

• External temperatures affect metabolism as well

• As external temperatures decrease, tremendous
  heat loss can occur
• As body temperatures are reduced, it becomes more
  difficult to generate metabolic heat

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Thermoregulation

• Internal body heat heat produced heat
  transferred or
• Body heat heat produced (heat gained heat
  lost)

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Thermoreguation

• Four mechanisms of heat transfer
• Radiation no direct contact e.g., Sun
• Conduction direct transfer of heat from one
  object to another
• Convection involves movement of gas or liquid
• Evaporation energy loss, conversion of liquid ?
  gas

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Thermoregulation
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Thermoregulation Ectothermy vs. Endothermy
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Endothermy vs. Ectothermy

• Ectothermy
• Lower energy requirements (more efficient at
  converting energy into biomass)
• Typically limited to diurnal environments,
  tropical and semi-tropical environments, short
  bursts of activity

• Endothermy
• May be active at night in tropics to the poles
• Very high energy requirements

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Thermoregulation

• Organisms have evolved adaptations to regulate
  their body temperature (and reduce heat loss to
  their environment)
• Changes in surface area, temperature difference
  and heat conduction
• In Ectotherms
• Presence of antifreeze (cold temps)
• Different enzyme systems (hot temps)

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Thermoregulation

• In Endotherms
• Increase muscular activity shivering (cold
  temps)
• Adjusting blood flow through skin (cold or hot)
• Adjusting amount of heat loss through evaporation
• Adjusting amount of insulation
• Adjusting proportion of body parts in order to
  reduce or increase surface area

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Thermoregulation
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Thermoregulation

• Adaptations to regulating temperatures can be
  both physiological and behavioral
• Most invertebrates (ectodermic) use behavior to
  adjust their temperature
• Orientation of body
• towards sun
• Shivering

www.flickr.com/photos/fxd/2760414614/
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Countercurrent Heat Exchange

• Vertebrate ectoderms, as well as some endodermic
  birds and mammals regulate their internal body
  temperature by way of a counter-current heat
  exchange system
• Warm blood pumped from within the body is used to
  warm the cooler blood returning from the
  extremities
• Ingenious! Blood leaving the warm interior loses
  its heat to returning vessels just before they
  enter (cooler) extremities

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Countercurrent Heat Exchange
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Countercurrent Heat Exchange in Action!!!
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Countercurrent Heat Exchange in Action!!!

• Marine birds do this as well!

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Countercurrent Heat Exchange
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Common dolphin dorsal fin
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Common dolphin dorsal fin
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Common dolphin dorsal fin
vein
artery
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Thermoregulation

• In general, ectotherms have low metabolic rates,
  which has the advantage of correspondingly low
  intake of food
• Some endoderms can prevent overheating by
  perspiring (sweating) and panting
• Mud baths are particularly useful in preventing
  overheating

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Adaptations to Temperature Extremes

• When temperatures fall below a critical
  threshold, the animal must resort to
  thermogenesis, the use of normal energy
  metabolism to produce heat
• Shivering (muscular activity)
• Nonshivering thermogenesis
• Occurs primarily in brown fat (hibernating
  animals, babies, arctic mammals)

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Adaptations to Temperature Extremes

• In mammals, thermoregulation is controlled by the
  hypothalamus
• When the temperature of blood exceeds 98.6F,
  neurons in the hypothalamus detect the
  temperature change, stimulates its heat-losing
  center
• Causes dilation of peripheral blood vessels,
  bringing more blood to the surface to dissipate
  heat
• Stimulates sweating suppression of
  metabolism-stimulating hormones

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Adaptations to Temperature Extremes

• When the temperature of blood falls below 98.6F,
  the heat promoting center of the hypothalamus is
  stimulated
• Causes constriction of blood vessels
• Inhibit sweating
• Epinephrine produced by adrenal medulla to
  stimulate metabolism

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Adaptations to Temperature Extremes

• Torpor decrease of metabolic rate over a
  relatively short period of time
• Reduces the need for food intake by reducing
  metabolism
• More common in smaller animals larger animals
  have too much mass to effectively cool

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Adaptations to Temperature Extremes

• Hibernation drastic decrease in metabolic rate
  over a long period of time, in response to colder
  temperatures
• Effective only in midsize animals
• Too big costs more energy to increase
  temperature than what is saved over winter
• Too small cant store enough energy
• Estivation large decrease in metabolic rate
  over a long period of time, in response to hotter
  temperatures ( food, water supplies)

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Thermoregulation

• Fever an increase in body temperature to levels
  above normal
• Considered to be one of the bodys (normal)
  immune mechanisms to inhibit the growth of
  bacteria or viruses
• Extremely high fevers, however, are detrimental
  and can result in seizures and hallucinations