Table 81.1 Thermoregulatory responses Figure 81.2 The fever cycle Figure 81.3 The tie course of a typical febrile episode From Pocock G and Richards CD. (2004) Human Physiology: The Basis of Medicine, 2nd edition. With permission of Oxford University Press Fever is defined as a rise in temperature above the normal range ‘set-point’ that is not associated with exercise or a high ambient temperature (Pocock and Richards 2004). It is one of the most common symptoms of illness in children (NICE 2007). To facilitate an understanding of fever it is necessary to review the key points associated with thermoregulation. The maintenance of a constant core body temperature is vital for normal cell function, as the rates of all metabolic processes are highly temperature dependent (Pocock and Richards 2004).
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The feverish child
Thermoregulatory responses to cold (body warming mechanisms)
Vasoconstriction
Shivering
Increase in basal metabolic rate (BMR) mediated by adrenal medullary and thyroid hormones
Warmth seeking behaviour
Thermoregulatory responses to heat (body cooling mechanisms)
Vasodilatation
Sweating
Decrease in BMR
Cold seeking behaviour 
Fever
Thermoregulation
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