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Temperature Regulation

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

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Temperature Regulation

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  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.

  4. 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

  5. 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

  6. Body Skin Environment Basal metabolic rate Muscle activity Shivering Vasomotor Sweating Piloerection Conduction Convection Radiation Evaporation Balance

  7. Core Temperature

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

  9. Balance hypothesis Response warm cool Feedback Controlled system Feedback

  10. Inputs Outputs Central thermosensors Neural sweating shivering vasoconstriction vasodilation warm warm cool cool Hypothalamus Peripheral thermosensors Hormonal adrenaline TRH

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

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

  13. 37.4 Postovulatory Rectal temp OC 36.8 Preovulatory 36.2 12 18 24 6 12 Time And the menstrual cycle (o- p+)

  14. 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.

  15. 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.

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

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

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

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