1. Announcements Turn in “Personal Information” on front table
Complete Knowledge survey on-line before 9 pm Monday
Community of Scholars Research Symposium
Saturday Sept 12
10 wks paid research on topic of your choosing!
Consider COS for Summer 2010

2. 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.

3. Physics of thermal energy flow
Cell metabolism= main source of heat
Is cooling more effective if sweat is toweled away?
Answers from Physics Professor Dr. Salley

4. Mechanisms of thermoregulation For constant body temp heat in = heat out
Reflex arc
Negative feedback
Examples
Acclimatization vs. adaptation

6. Negative Feedback Loop

7. Central thermoreceptors
Add covers or clothing or enter sleeping bag
Conductive heat loss
Radiative heat loss
Convective heat loss
Skin temp
And Core body temp
Detected by thermoreceptors in skin
Central thermoreceptors
Activity in sensory nerves
Cerebral cortex
Somatic nerves
Hypothalamus
Voluntary behaviors
Sympathetic nerves
Relax smooth muscle in cutaneous arterioles
Remove covers Turn on fan, etc via
Somatic nerves
Muscle tone
Skeletal Muscles
Sweat Glands
Sweat production
Evaporative heat loss
Heat production
Heat loss
Blood flow to skin
Core temp.
Heat loss by conduction & radiation

8. 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)

9. 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?

10. Central thermoreceptors
Add covers or clothing or enter sleeping bag
Conductive heat loss
Radiative heat loss
Convective heat loss
Skin temp
And Core body temp
Detected by thermoreceptors in skin
Central thermoreceptors
Activity in sensory nerves
Cerebral cortex
Somatic nerves
Hypothalamus
Voluntary behaviors
Sympathetic nerves
Relax smooth muscle in cutaneous arterioles
Remove covers Turn on fan, etc via
Somatic nerves
Muscle tone
Skeletal Muscles
Sweat Glands
Sweat production
Evaporative heat loss
Heat production
Heat loss
Blood flow to skin
Core temp.
Heat loss by conduction & radiation

11. p. 595 Fig 16-19 Explain “chills” at onset of a fever
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?
Central & Peripheral Thermoreceptors
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

12. Are negative feedback loops subject to modification?

13. 1st day on the job 10th 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, this is Feed Forward (requires experience). FF is evidence of Acclimitization.