Thermoregulation

Thermoregulation regulates body temperature. Skin signals can anticipate a change of core body temperature, so a response need not wait for an internal error. ^[ref]

These responses have costs and environmental limits. Shivering consumes metabolic resources; cooling through sweating removes water that must eventually be replaced. High humidity restricts evaporation, so secreted sweat and successful cooling are not interchangeable. Maintaining core body temperature also depends on maintaining circulation: depleted blood volume can compromise skin blood flow and heat transfer. Seeking shade or reducing work changes the disturbance itself, whereas a larger regulatory command merely attempts to counter it. ^[ref]

The effective rate of heat transfer per body-to-environment temperature difference. Insulation, posture and perfusion can change it.

Production of heat through metabolic processes.

heat production through mechanisms other than shivering. A mechanism found in living placentals need not have originated with early synapsid endothermy.

A thermogenic tissue of many placental mammals. It should not be assumed to be the ancestral heat-producing mechanism in every synapsid.

heat generation through muscle activity associated with shivering.

Variation of body temperature across times or body regions. An endothermic animal need not maintain one constant temperature continuously.

Dependence primarily on external heat sources for body-temperature regulation, without implying an inability to regulate temperature behaviourally.

Maintenance of a relatively constant body temperature. It differs from the metabolic source of heat described by endothermy.

Core body temperature refers to internal temperature, distinguished from skin temperature. Different measurement sites are proxies with their own limitations, not interchangeable readings of a perfectly uniform interior. ^[ref]

Twelve resting volunteers wore a water-perfused suit. Tubes covered the torso, upper arms and legs; the right forearm remained uncovered for laser Doppler blood-flow measurement. Six thermocouples estimated mean skin temperature; a sublingual thermocouple measured oral temperature. A dry-air capsule measured local sweat output from outgoing air moisture. ^[ref]

After two control scans near $34{}^{\circ }\mathrm{C}$ skin temperature, the suit cooled and then warmed the skin. Mean oral temperature was $36.6{}^{\circ }\mathrm{C}$ during both cooling and early warming; mean skin readings were $30.5$ and $38.2{}^{\circ }\mathrm{C}$. Cutaneous vascular conductance fell during cooling and rose during warming. The inference is that compensatory blood-flow responses can precede an appreciable internal temperature change. ^[ref]

Repeated baselines controlled comparison within participants; closed mouths reduced oral-probe cooling artifacts. A later control with reduced oral temperature was excluded. Oral temperature is a proxy, local flow is not whole-body heat transfer, and the fixed condition order leaves time effects possible. Brain imaging measured regional blood flow, not direct neuron firing or causal necessity. ^[ref]

Sweating supports thermoregulation through evaporation of water, which carries away latent heat.

Historical grouping of sustained febrile illnesses. It is broader than typhoid fever; characteristic enteric lesions cannot be assigned to every illness historically placed in the group.

An instrument comparing dry-bulb and wet-bulb temperature to investigate atmospheric humidity.

Relative humidity is the ratio of the partial pressure of water vapor to its saturation vapor pressure at the same temperature, usually expressed as a percentage.