1. Temperature Regulation The Reverend Dr. David CM Taylor http://pcwww.liv.ac.uk/~dcmt/Tempreg.ppt

2. Why temperature regulation? (The 19th century experiences of puerperal fever and the hospital as a ‘gateway to death’ are historical reminders of advances made.) “Birth is big for babies too - many changes. …Keep Baby warm.” In the postnatal ward, Mrs Cheung asks, “Can I feed her? Why are you taking my temperature? I’d like my aromatherapy!”.

3. What we will cover Triggered by elements in the case scenario we will consider: Why we regulate temperature? What is meant by “normal” body temperature What mechanisms there are for regulating body temperature (and the importance of behavioural mechanisms. How babies are different from adults. How fever occurs.

9. Why? All organisms are limited by their ability to survive in different temperatures Some, like reptiles and amphibia are poikilothermic Others like humans are homeothermic

10. How? The actual body temperature is a consequence of the balance between the amount of heat produced and the amount of heat lost. The balance may be altered physiologically or behaviourally

11. Basal metabolic rate Muscle activity Shivering Vasomotor Sweating Piloerection Conduction Convection Radiation Evaporation BodySkinEnvironment Balance

12. Core Temperature

13. Reference Response Controlled system Feedback Set-point hypothesis So how is it regulated?

14. Response Controlled system Feedback Balance hypothesis Feedback warm cool

15. InputsOutputs Hypothalamus Central thermosensors warmcool Peripheral thermosensors warmcool Neural sweating shivering vasoconstriction vasodilation Hormonal adrenaline TRH

16. Babies Babies (and hamsters) have an extra mechanism Brown fat. Suprascapular deposits Rich in mitochondria

17. Normal body temperature Depends where and when you measure it tympanic> oral > axillary by 0.5 o C can be affected by exercise emotion time of day

18. Rectal temp O C 37.4 36.8 36.2 121862412 Time Postovulatory Preovulatory And the menstrual cycle (o- p+)

19. Fever monocytes and phagocytes release endogenous pyrogen (Interleukin-1, IL-1). The anterior hypothalamus is sensitive to IL-1 Hypothalamic sensitivity to temperature is altered.

20. So… The body temperature then becomes regulated at a new, higher level. There is some evidence that the raised body temperature enables the fight against the infection.

21. But... Every 1 O C rise in temperature increases basal metabolic rate and oxygen consumption by about 13%, In acute infection, the ability to mobilise fat stores is inhibited.

22. Consequently Skeletal muscle is broken down and the amino acids are used in gluconeogenesis. This can be debilitating.

23. And even worse In addition to the increased demand for energy Temperatures (above 42 O C) damage nerve cells impair thermoregulation have more serious consequences.