The Development of Circadian Rhythms in Human Infants

temperature is one of the most tightly regulated systems in the body. Deviation from
„normal‟ physiological development, as characterised by the development of adult
mature temperature pattern during sleep, may be a marker for future morbidity,
mortality or be the basis for increased vulnerability such as to the disease entity
known as SIDS.
1.5.1 The Mechanism of Thermal Regulation
The hypothalamus is responsible for the neuronal control of core body temperature.
Peripheral receptors send signals to the posterior hypothalamus at the level of the
mammillary bodies. These signals integrate with those from the anterior
hypothalamus to regulate body temperature.
Body temperature is lowered by several methods: vasodilation of peripheral blood
vessels, sweating and a decrease in metabolism. Conversely, temperature is raised in
response to low temperatures by vasoconstriction, piloerection and the generation of
heat by processes controlled by the sympathetic nervous system.
Core body temperature is maintained within a strict, narrow and precise range of +/-
0.6º Celsius, which is critical for enzyme function. There is a set point of 37.1º
Celsius above which heat is conserved and below which heat is produced. This
occurs in order to maintain a normothermic environment. Temperature only changes
in response to a significant insult such as illness, vaccination or profound
hypothermia.
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