文档介绍：Fever
Fever
Normal body temperature:
37oC, Circadian variation <1o C
Definition of fever:
An elevation of core body temperature above the normal range
rectal T > oral T 0. 5oC > axillary T(腋温)
Fever
Hyperthermia (体温过高)
fever due to a disturbance of thermal regulatory control
excessive heat production
decreased dissipation
loss of regulation
Pathophysiology
Body temperature is determined by two opposing processes
heat production heat loss
They are regulated by the central nervous system
Energy in the form of heat is generated by living tissues (thermogenesis)
Energy may be passively absorbed from the environment and transfer the energy to the surrounding medium
Pathophysiology
The body temperature is under control of the preoptic area of the anterior hypothalamus(下丘脑)
Thermostat (恒温器)
It receives input from both central receptors and peripheral receptors
Heat production and heat loss
Basal metabolic rate is controlled by hypothalamus, by varying the level of circulating thyroxine (肾上腺素)
Increased muscle sensitivity (shivering)
By varying the volume of blood flowing to skin’s surface (>100 fold)
By vaporization (exocrine sweating)
Set point
370C
390C
Heat Production
Heat Loss
Heat Production
Heat Loss
Pathophysiology
Elevation of body Temperature
shivering thermogenesis and dermal vasoconstriction
sympathetic outflow
Cooling mechanism
sweating and dermal vasodilation
mixture of sympathetic and parasympathetic pathways
Pathophysiology
Hypothalamic thermostat
Set point: 37oC
lowest: 4 ; peak: 6~10
Fever follow this pattern
Factors affect body Temperature
exercise
menstrual cycle
environmental temperature
Pyrogens
Neuroimmunoendocrine
Substances that can cause fever
Either exogenous or endogenous