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The Challenge: Melting these 6 ice cubes as fast as possible. How to do it? Make these 6 ice cubes last as long as poss PowerPoint Presentation
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The Challenge: Melting these 6 ice cubes as fast as possible. How to do it? Make these 6 ice cubes last as long as possible? How to do it? Modes of Heat Exchange: Conduction Convection Radiation Evaporation Modes of Heat Exchange:

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slide1

The Challenge:

Melting these 6 ice cubes as fast as possible. How to do it?

Make these 6 ice cubes last as long as possible? How to do it?

slide2

Modes of Heat Exchange:

Conduction Convection Radiation Evaporation

slide3

Modes of Heat Exchange:

Conduction Convection Radiation Evaporation

slide5

Modes of Heat Exchange:

Conduction Convection Radiation Evaporation

slide6

Modes of Heat Exchange:

Conduction Convection Radiation Evaporation

slide7

Modes of Heat Exchange:

Conduction Convection Radiation Evaporation

slide8

Modes of Heat Exchange:

Conduction Convection Radiation Evaporation

endotherms and ectotherms

Endotherms and Ectotherms

Endotherms regulate core body temperature near a set point.

Ectotherms do not achieve a constant body temperature; body temp approximates the temperature of the environment.

slide11

Convective heat loss

Conductive heat loss

Skin temp

Radiative heat loss

Cerebral cortex

Detected by thermoreceptors in skin

Hypothalamus

Heat loss

Sympathetic nerves

Sweat Glands

Muscle tone

Heat production

Relax smooth muscle in cutaneous arterioles

Activity in sensory nerves

Blood flow to skin

Sweat production

Evaporative heat loss

And Core body temp

Heat loss by conduction & radiation

Core temp.

Add coversor clothingor enter sleeping bag

Voluntary behaviors

Remove coversTurn on fan

Somatic nerves

negative feedback loops what to look for
Negative feedback loops: What to look for
  • The stimulus (temperature, etc.)
  • Sensors (thermo-, chemo-, photo-, mechano- receptors
  • Afferent pathways to integrator (may not exist)
  • Integrators (typically neurons or endocrine cells)
  • Efferent pathways from integrator
    • nerves
    • hormones
  • Effector cells or organs
    • virtually any cell
    • especially glands and muscles
  • The response (opposes stimulus)
slide13

Thermoregulation in a comatose patient?

In steady state: Heat gain = Heat loss

What if room temperature was increased or decreased?

What if additional covers were added to the patient?

slide14

Conductive heat loss

Skin temp

Radiative heat loss

Heat loss

Muscle tone

Heat production

Activity in sensory nerves

Evaporative heat loss

Sweat production

Blood flow to skin

And Core body temp

Heat loss by conduction & radiation

Core temp.

Add covers

Cerebral cortex

Detected by thermoreceptors in skin

Voluntary behaviors

Remove coversTurn on fan

Hypothalamus

Sympathetic nerves

Somatic nerves

Sweat Glands

Relax smooth muscle in cutaneous arterioles

p 595 fig 16 19

Central &PeripheralThermoreceptors

p. 595 Fig 16-19

If setpoint is reset to a higher temperature, then actual temperature is LESS THAN the new set point, so one feels “cold” and adds clothing, curls up, and shivers. These are “Chills.”

  • Explain “chills” at onset of a fever
  • Explain “sweat” when a fever “breaks”
  • How does Tylenol reduce a fever?

Tylenol and other non-steroidal anti-inflammatory drugs (NSAIDS) suppress the production of eicosanoids (IL-1, IL-6, etc) so effect of these on the set point in hypothalamus is minimized.

If setpoint is reset to a lower temperature or back to normal, then actual temperature is GREATER THAN the new lower set point, so one feels “hot” and removes clothing, fans, and sweats. These are “the sweats” when a fever breaks.

To reach new,

Higher set point

acclimatization
Acclimatization
  • 1st day on the job
    • Increase body temp….. Delayed sweating via negative feedback
  • 10th day on the job
    • Sweating precedes changes in core body temperature
    • and sweating is increased
    • And salt loss in sweat is minimized

Responses begin even before core temperature increases! Not just negative feedback.

acclimatization feedforward
Acclimatization & Feedforward
  • Deviations from set point are minimized
  • Learned (by experience)
  • Anticipates changes of a physiological parameter
  • Response begins before there is a change in the physiological variable
  • Minimizes fluctuations
slide19

~37oC

Be able to explain the physiology in each of these situationswith a detailed diagram of negative feedback responses!