In contrast to the core temperature, the skin temperature (shell), falls and rises with the temperature of the surroundings.
Thermoregulatory Impairment 
Hypothermia, defined as a drop in core body temperature below 35 C (95 F), results in initial/mild impairment in the body's thermoregulatory capacity. Greater impairment occurs with increasing severity of hypothermia; severe hypothermia is defined as core body temperature dropping below 28 C (82.4 F)
Part of the reason for this diminished regulation is that the rate of chemical heat production in each cell is depressed almost 2-fold for each 10 F decrease in body temperature.
Heat Illness Spectrum
Excessive core body temperature presents along with a clinical spectrum, with heat stroke presenting as an emergent clinical condition defined by a core body temperature exceeding 40 C (104 F)
Heat production is determined by metabolism.
The rate at which heat is lost is determined almost entirely by:
Anterior Hypothalamic-Preoptic Area in Thermostatic Detection of Temperature
Posterior Hypothalamus Integrates the Peripheral and Central Temperature Sensory Signals
Detection of Temperature by Receptors in the Deep Body Tissues
Detection of Temperature by Receptors in the Skin
Blood Flow to the Skin from the Body Core Provides Heat Transfer
Effect of the environmental temperature on heat conductance from the body core to the skin
Basic Physics of How Heat Is Lost from the Skin Surface
Heat dissipated by radiation, evaporation, and conduction.
Evaporation and conduction of the air are accelerated by convection.
Evaporation Is a Necessary Cooling Mechanism at High Air Temperatures
Clothing Reduces Conductive and Convective Heat Loss
Set Point for Temperature Control
Sweating and Its Regulation by the Autonomic Nervous System
Mechanism of Sweat Secretion
The sweat gland consists of two parts: the duct that passes through the skin and reabsorbs salt and water, and the deep subdermal coiled gland that secretes the sweat.
Sweat gland secretes a fluid called the precursor secretion; the concentrations of constituents in the fluid are then modified in the duct.
Hypothalamic Stimulation of Shivering
Sympathetic “Chemical” Excitation of Heat Production
After following the standard ATLS resuscitation protocol (airway, breathing, circulation), the next step is to cool the body to reduce core body temperature rapidly. Whole-body cooling units on-site should be utilized. As long as the patient is stable, the rapid cooling protocol takes priority even before transportation to the local emergency department is commenced.
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