Paid Research Opportunity: Endotherms and Ectotherms - Community of Scholars Symposium

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 ProfessorDr. Salley

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

6. Negative Feedback Loop Negative feedback

7. Convective heat loss Conductive heat loss Skin temp Radiative heat loss 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 Central thermoreceptors Cerebral cortex Somatic nerves Voluntary behaviors Remove coversTurn on fan, etc via Somatic nerves Skeletal Muscles

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. Convective heat loss Conductive heat loss Skin temp Radiative heat loss 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 Central thermoreceptors Cerebral cortex Somatic nerves Voluntary behaviors Remove coversTurn on fan, etc via Somatic nerves Skeletal Muscles

11. 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

12. Are negative feedback loops subject to modification?

13. 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, this is Feed Forward (requires experience). FF is evidence of Acclimitization.